Boost tabs are aerodynamic devices that take away lots of the load of the surfaces. As the surfaces move in one direction, boost tabs force a smaller control surface attached to the larger control surface (see picture) to move in the opposite direction, creating a force that helps the surface.
A while ago somebody posted a thread about installing boost tabs on his airplane (a 40% Yak, I think). He said that using multiple high-power servos (and high-current batteries) was a waste of money and weight because boost tabs are so awesome. Also digital servos are a waste of money because boost tabs "give you all the holding power you need" (which doesn't make any sense; boost tabs reduce the restoring force created by control surface movement, which would lead to decreased stability, which would require more holding force. Besides, the real value of digital servos is accuracy, programability, and resolution).
Anyway, the thread poster didn't respond well to criticism or questions about trusting a 40% airplane to a few cheap servos and wasn't very respectful to the moderators. The whole thread went downhill fast and was closed. So now boost tabs are a huge joke on FG, not because of their actual viability but because that thread was just so hilarious.
To answer the original questions from this thread, my vote goes with the 7950. I have four on the ailerons of my 40% Carden and they work great. Some people claim that they jitter when run at unregulated lithium voltage, but mine are regulated and I have yet to experience this. I have two 8711's on the rudder and they work very well but have developed considerable gear slop whereas my Hitec servos have not. I have a friend who has used 8711HV's, and they worked great until they stripped during an IMAC contest.
I have not used the Futaba servos but I have had such great experiences with my Hitec stuff that I wouldn't really consider anything else. I'm not saying it isn't viable, just that I use Hitec because I believe it is the best.