Hi, I want to create a community based site. Which of the above 2 are the best and why? Really appreciate any input. Thanks
The bigger question is, what CMS do you prefer? Joomla or WordPress? And, what's your budget? BuddyPress is free. Jomsocial is around, oh, $150 USD for the version that doesn't have a link-back to the developer. I would suggest you stay away from Mighty Touch unless they have removed Ion Cube. I NEVER, EVER recommend running encrypted software on your server.
I don't recommend Mighty Touch. I've used both BuddyPress and JomSocial and like them both. BuddyPress is a lot easier to work with, but is much less flexible. If you're going to have a large community, my vote is for JomSocial. They're having a $45 special (~70% off!) until this Saturday... You should email them asking about it so you can get in on it!
These two are kind of different. They suit different needs. BuddyPress is much closer to Twitter, while JomSocial goes the Facebook direction. It depends what kind of site do you want to create...