For the past month, I've been carrying around a Blitz Needle. Individual shots are pretty weak, but they are really handy for Silkwings and Greavers, especially when you have the luxury of distance to ready your shot. You can't move around while shooting, which is why I have started to appreciate the Antigua, and I look forward to expanding into that line.
I haven't tried the others you mentioned, but they are each described on the SK Wiki: http://wiki.spiralknights.com/Handgun
I haven't handled the Valiance yet, but based from my experiences the Blaster is good for those who don't have time to elaborate over weaknesses and strengths. It provides mobility while firing and reloading, and deals good amounts of normal damage. Valiance is pretty much the same. :v