I've always been with Emerald - then Phoenix. Loved it...no problems...utterly disliked everything about the Viewer2 interface. But then I heard that Phoenix will be coming to an end - and that users should go ahead and start "getting used to" Firestorm. So I download it, only to find it is nearly identical to Viewer2. Following the advice of the developers, I spent a couple of weeks "getting used to it" - mostly editing the interface to make it less like Viewer 2 (not all that successfully, despite what I've heard about THAT), and getting the graphics to look ok.
Well, yesterday I finally got fed up with all the Firestorm bugs and started to look around for what else is available. After coming up short everywhere else, I downloaded Viewer2 again. I figure..if it's gonna look like Viewer2 anyways, why not just go back to the (hopefully less buggy) original?
Here's my take:
-Viewer2 and Firestorm both have the multiple attachment points and multiple LAYERS. After trying this, I can't seem to live without it.
-Both viewers have a Favorites bar for quick TPs to your commonly used sims. Awesome.
-Firestorm is definitely more customizable, and you can dock the nearby chat with group chat windows. Right now that's my main peeve with V2 - why two chat windows?
-Radar in V2 doesn't let you perv, and Firestorm makes it much easier to cam inside objects.
-But V2 is functioning and not crashing...so for now, that wins out over the few extra conveniences Firestorm has. I'm still going back and forth - perhaps Firestorm will fix some more bugs and become my future choice.