This guide is geared toward analyzing the components of a CS:GO crosshair, based on what some of the pros use.
Take for example, the shape of an average crosshair. Usually, you'll see 4 ends pointing outward and inward at the same time, in the shape of a T. But have you ever wondered why the t shape is so commonly used over another shape, such as a circle?
For starters, all 4 ends of the crosshair, as I mentioned before, seem to be pointing inward, thereby gravitating your attention towards the center (it's also why you might see a small gap in the middle of the crosshair). This in turn, helps you focus on centering your shots, such as a headshot.
My guess is that our minds seem to pay more attention to patterns or consistency (such as the ends pointing inward toward one direction) rather than something a bit more random (such as the same ends also pointing outward in 4 different directions). Nevertheless, this crosshair also provides a boundary of some sort by covering all directions (left right up down) given it's natural shape (or t).
There's nothing wrong with a dot crosshair though; in fact it probably provides the highest degree of parallelism with respect to your opponent's head, given it's natural shape. My main concern however (as I used to use one) is visibility and direction, meaning the dot is just there, but it does not "guide you or shift your focus toward the center, like a t-shape crosshair would. Least, that's the way I see it.
Nevertheless, I respect personal preferences, and this is just a small snippet of some of the crosshair features to look for or think about.
Full article (I wrote) can be found here: Top CS:GO Crosshairs (imo)
Lastly, if you have any comments or suggestions, feel free to share them. Thanks.