Im talking about usefullnes and practicality here, no fancyful crosshairs. I personally like circle(1), but i wonder if there's a better one?
I just use a plain cross personally, changing the color every so often (I think it's white at the moment, though it has been bright pink-- to stand out more ;P). It can be difficult to aim the pinpoint-accuracy weapons with the more elaborate crosshairs, though it can be a little easier to see where you're placing your rockets. You won't get much skill improvement that way however. So my advice is just make sure it's something colored/large enough that you never have to actually find the crosshair, and shaped so you don't even have to think about hitting the centre.
[COLOR=black]I use the custom crosshair thing so I could change crosshairs for different weapons, like shock rifle and sniper rifle I gave smaller cross’s, but once you check that box it has pretty good ones already set, I just changed some of the colors, I like having the crosshair change when I go from a Minigun to a sniper rifle. Works good for me.[/COLOR]
Honestly, they all work fine for me. I don't really have a preference, though the Redeemer/Ion Painter/Target Painter one is nice.