OK guys, from my own experience, I'll try to make a little comparison between the Razer Abyssus and the Zowie AM, to find out what is the best mouse between these two. OK, there you go :

Design and quality of the components:
ADVANTAGE AM!
It was kind of a hard decision to make, because I think that both mice look great and the components are of good quality for both mice. However the feel of the mice is different, I mean, the abyssus seems to be made of cheaper components than the AM. Overall the AM feels a little bit more solid and reliable. But keep in mind that the AM is more expensive, ~25€ more expensive as far as I know. Also, I don't know about the abyssus, but the AM does have omrons and huanos switches, means that the buttons are solid and will last longer.
I have an Abyssus mirror edition, and all I have to say is that it looks very nice. I like the glossy top of the mouse. For the AM, I would choose either the full gloss version (it just looks amazing, especially in full white!), or the rubber one. I personally have a rubber one, and I like the soft feeling of the mouse, it's a real pleasure for the fingers!

Weight:
ADVANTAGE ABYSSUS!
From what I experienced, the abyssus seems a little bit lighter. Nothing really more to say there, if you want the lightest possible mouse, go for the abyssus. The difference is only minor though, and to be honest, both mice are light and won't stress your hand/fingers too much.

Shape:
IT'S A DRAW!
The abyssus is a bit larger, but the AM is a bit longer. The abyssus has a more agressive design, while the AM seems to be more comfortable for your fingers, altho I would say that the abyssus is actually less stressful for your fingers, after a long session of gaming, paradoxaly. Only depends on the way you hold your mouse there, I guess. For some people, the abyssus feels more comfortable, while for other people, it's the AM. If you have a sweaty hand, I would recommend the abyssus because it's easier to fully hold the mouse and get a good grip on it. Maybe I should try the Zowie FK, would probably suit my finger type grip better. Anyway, altho being different, I personally like both shapes in their own way. I would say that the abyssus is pretty close to the Logitech mx300/G1/G3/G100(s), and quite close to the kinzu, but there again, with a more agressive shape. On the other hand, the AM is pretty close to the WMO/IMO 1.1a, with sides buttons, of course.

Scroll wheel:
IT'S A DRAW!
From what they say in the packaging, the AM does have a very solid scroll wheel, something that could last probably 2 or 3 years without breaking. From what I experienced, it does indeed feel nice and solid, but too hard for my liking. It's actually VERY hard to press it. On the other hand, the abyssus's scroll wheel doesn't suffer from any major issues/flaws, although, there again, I'm not sure if it could last more than 2 years without breaking. If you're looking for comfort, you might try the abyssus, whereas if you're looking for durability, you might want to try the AM.

Sensor and Lift-Off Distance (LOD):
LITTLE ADVANTAGE AM!
I've played with the abyssus for something like 11+ months, coming from a Steelseries Kinzu. At first I needed time to adapt to a non-prediction non-hardware accel mouse, but once I got used to it, I realized that the abyssus's sensor is definitely better than the kinzu's one. I'm not a Counter-Strike player, but still, I do not like accel at all. I'm just looking for a mouse which would read my mouse's movements on the mousepad at perfection, I'm looking for a "pure" sensor without any angle-snapping/prediction and so on.
The Avago ADNS-S3888 inside the abyssus is very close to perfection in that regard. However, what I do not really like after trying the AM, is the LOD of the abyssus. The AM has such a low LOD that it's almost impossible to go back to your previous high LOD mouse. I did a little test after playing with the AM for approximately 1+ month; I plugged in my old abyssus again, and guess what, I wasn't aware of such an issue before, but when you experience the low LOD of the AM, you just realize that a high LOD can be quite a serious flaw. I'm not saying that you just can't get used to a high LOD, basically you can get used to anything really, but still, a high LOD can be a pretty serious issue if you play with a low/very low sensitivity. That being said, I still like the abyssus sensor A LOT.
Now let's talk about the AM sensor. I have three words to describe it : pretty much perfection. The Avago ADNS 3090 sensor is pretty much flawless, you can make very slow as well as very fast movements without any loss in precision. I won't talk to much about this sensor because I think that almost everyone knows how good it is already. And like I said, the low LOD combined with a flawless sensor is a perfect combo, to be honest.

DPI and polling rates:
ADVANTAGE AM!
Let me remind you the DPI steps of the AM and abyssus. For the AM : 450, 1150 and 2300. For the abyssus : 450, 1800 and 3500. I tried the abyssus at both 3500 and 450dpi. But if I play with 3500dpi, I have, of course, to lower the ingame sensitivity A LOT (something like 0.4 to have approximately 30cm/360°). And to have an almost perfect 30cm/360° with 450dpi, I have to set up my sensitivity to 2.8. To be honest, I get pretty much exactly the same feeling at 30cm/360° with both 450 and 3500dpi. Didn't try high sensitivity with 3500dpi though.
Then with the AM I tried both 450 and 2300dpi. Except that, not like with the abyssus, I actually tried med/high sensitivity with 2300dpi. What I consider a med/high sensitivity is something under 20cm/360°. Actually it was exactly 16cm/360°. And to be honest, I liked the feeling of it!
So, basically, if you're a low sensitivity player, you might want to play with a low DPI, while if you're a high sensitivity player, you might try higher DPI.
Having said that, both mice work really great at both low and high DPI, only a matter of preference, but I would still recommend 450dpi nevertheless because in some games, it's not possible to have a sensitivity under 1, keep that in mind ;). At least if you're a low sensitivity user.
About the polling rate, well, nothing much to say there, just play with 1000hz, by default on the AM. The abyssus doesn't have a 500hz incrementation though, something that some people would miss.
Also, I prefer the way of changing DPI/polling rate with the AM than with the abyssus. For both mice, changing DPI can be done below the mouse, except that with the AM you have to press 1 button and then see the color of the little led close to that button to know how much DPI you have. For example, a red led means 450dpi and a blue led means 2300dpi. Genius! And if you want to change the polling rate of the AM, you just have to press a combination of button right before pluggin in the mouse! Works like a charm.
In the matter of the abyssus, the dpi/polling rate steps located below the mouse might be easily breakable if you move them too hard.

Mouse's skates:
ADVANTAGE AM!
I don't really like the skates of the abyssus, because I think that they are too small. I personally prefer large mouse's skates over small ones, even though it adds a little bit more friction. I also liked the fact that with the AM, they give you some additional mouse's skates.
And in term of feeling, well, both mice slide on the mousepad without interruption, with smoothness. They are pretty equivalent in that regard.

FINAL RATING:
If I had to rate these mice, I would give a 9 out of 10 for the AM, and a 8.5 out of 10 for the abyssus. So far the AM is probably the best mouse I have ever used, and the abyssus comes second right after it.
However, if you only have a low budget (in other words, if you are poor like Jamerio), go for the abyssus, you won't be disappoint. For this price's range the abyssus is probably the best mouse you could get, along with the g100s from Logitech. If you are a palm grip user, forget the abyssus though... And go for a DeathAdder from Razer or even an EC1/EC2 Evo from Zowie.