That's the tricky thing about these comparisons, we all have different computers so a true test is not really possible. Where one user crashes and takes 2 minutes to rez the people at the hub, another has great performance and vice versa when they switch.
I'm going to try to compare just on features, but then that's a personal preference too. Not everyone wants or needs the same thing but I'm still trying to compile a list at least so it's easier for people to pick based on the features they want.
Right now, other than being very bright in some places, I'm personally leaning towards Nirans as my new viewer.
I love the UI (FUI), being able to move my buttons to the top felt right to me immediately. The Navigation area instead of menus was immediately intuitive to how my brain works apparantly because I found everything there right away. The deciding factor though is the smooooth camera movements. Second Life has never "felt" like this before. It's like I'm floating in space or in some sort of flight simulator game. It's hard to explain but I love the effect of camming around with Nirans and I'm excited to get back to my machinima attempts now.
Other than the brightness, which I asked about and the creator gave me some tips about my settings that I need to try, Niran's makes my SL look like nothing I've ever seen before and I'm in awe just standing in my house. I can't wait to explore some sims and play with photos.
One thing to note about Nirans, having your graphics on High is equivalent to Ultra in the other viewers so if you go ultra on Nirans..
This post was really helpful to me when I switchedhttp://modemworld.wordpress.com/2011/12 ... different/
And an idea how it feelshttp://www.youtube.com/watch?v=a5nbMl19FVI