One of the big conversations on SL is about which viewer you should use and why.
People have their favorites based on features, looks and usability, but you should probably try them out and pick one that fits you best. I have used V2, Phoenix and the official viewers. Many say that Phoenix is best if you want to do building stuff. But I actually do well with the others too. For InWorldz I use Imprudence, it looks a bit more basic but works well.
Prim perfect is doing reviews on the 3rd party viewers, take a look.
Prim Perfect’s Guide to Third Party Viewers: The Basic: Second Life 1.23.5
Prim Perfect’s Guide to Third Party Viewers: The Future? Second Life Viewer 2