I only use FBI so it's what I voted for. The network install is nice when your SD card is almost full so you don't have double the space of the game.
I installed MH in about 35 minutes so I don't have the speed issues some seem to have.
I'm form the dinosaur days of playing PC games on DOS so the interface is actually welcoming to me.
Have not had any issues with it so far, even DLC I have installed worked great so I have not really had a, reason to look elsewhere.
However, most CFW guides have you install FBI, so it would be interesting to see the difference between people like me that just use it because it's already there and it works so why bother, and people who actively go for an alternative as soon as CFW is up and running.
It kind of like the Internet Explorer deal, a good majority of people using it do so because it's already there and it works so that attributes to the usage stats, whereas most proficient users see its only use as the way to download their browser of choice.