The big difference between Azureus and Limewire is the advanced packet encryption methods that client like Azureus are capable of.

It is very possible that a ISP trying to block a user from using P2P will not be able to block Azureus. Don't get me wrong, some are very capable of doing so, but this would take pretty advanced and newer "shaping" methods. Also Azureus and uTorrent developers are constantly making improvements on their encryption methods. Limewire on the other hand does no such thing.

One reason for this in that LimewireLLC is US based, meaning that they are not untouchable, while the open source multinational free BitTorrent developing and distribution is not bound to any country.

These programs are so different. Like day and night. Limewire will be releasing a client that will support torrents in the near future. This may change things encryption wise.

As you probably know, Limewire has been sued by a collection of major recording industries and has counter sued them. Unlike the other P2P clients that have gone bye bye in the last few years LimewireLLC has the power to put up a fight instead of crumbling into some settlement that would ultimately be the end of it.

This is in large part because of the money LimewirePro has brought in but also due to other ways of making revenue. I think the Limewire client is not their only project (read that somewhere)