Weight?-- YES, there are some who will search for a lighter piston for a build, or even lighten them even more than what they are out of the box. HOWEVER, if you are asking this question YOU ARE NOT one that needs to worry about this. Quality of piston will be a much more important thing to you.
Finish?-- You mean cast or forged? There are SOME cast pistons out there that are decent, but at the end of the day its hard to beat a weisco for most builds
Comp ratio?-- WTF?? Banshees are 2 stroke and although there are some variation (flat top, crown, etc) the piston has little to nothing to do with your end comp ratio
Bore size?--Again, Im guessing that when you are asking questions like this you dont have a 95mm or bigger bore. Most every site sponsor here can get you pistons for whatever bore your needing from stock to any over bore or larger for aftermarket cylds.
Availability?--Any site sponsor will stock about any size your going to need. And if they dont have them on the shelf they will be able to get them in just a day or 2.