They are both the same so it doesn't matter both work the same for me, That is Basic LimeWire and frostwire. Most of the time I use LimeWire Pro if you have a high speed connection it is better than basic or frostwire.
If you want LimeWire Pro use basic for a while to make sure you like it. Basic is free and Pro cost $18.88 for Pro and 6 months of free upgrades.
When and if you get Pro save the installer to your hard drive or burn it to disk. Because after the 6 months is up you will not be able to get another copy of it from LimeWire.
As far as online installer or offline try the online first if it wont install then use the offline installer.
You can get limewire or frostwire at the link's below make sure you only get limewire or frostwire from the official sites.
http://www.limewire.com/english/content/download.shtml http://www.frostwire.com/