The cool thing with a Sabertooth or other "dual" speed controllers, is that they mix fwd/bck/lft/rgt a lot more reliably than having a single controller per motor and then using a separate mixer. They tend to be a bit dearer, but you will end up with an extremely simple setup i.e. receiver, speedo and battery. Job done.

The Sabertooth's aren't as posh as the XXL's and Vantecs, but then they're half the money. I've been using a Sabertooth 2x12 for ages and even in a recent event and it hasn't given me any jip. I love anything simple and easy to use so Sabertooth suits me. As mentioned above, some folks hate them, some folks will tell you that Botbitz's are the mutts nutts. It's just whichever you like the look of. Most items in a robot take a beating and will need replacing as time goes on so I will usually just buy whatevers cheap lol. But yeah, to sum up the ramblings I recommend the dual controllers for the simplicity factor.