You can check out the changelog here

How much difference you'll see between Pro & basic depends a bit on your connection & what you're using LW for...Pro lets you connect to 2 extra ultrpeers, so it has the capacity for better search results. People who look for rarer files find it better. You'll also be able to connect to a couple of extra hosts when downloading (max 14 if you have a T3 connection).

You'll be able to save your Pro installer(s) & copy them to your other computer. Just remember to bookmark your personal download page & save & back up any installers you download...LW doesn't keep old installers for downloading later if you lose the current one.

If you haven't already, try the basic (free) version first. Get to know the app & work out if you like it enough to buy the Pro

Download either version only from www.limewire.com