As you've found out, you can run SL on a MacBook Pro. The viewer you use will, for the most part, depend on your personal preference. I' running both the Second Life viewer and Emerald on an iMac and on a MacBook, and both viewers run fine. I've tried SnowGlobe, and found it ran well too. As long as your Mac has a good/newer graphics card and enough memory, you should be ok. Try the different viewers, and see if one of them fits for you.