Anyone who worked on military aircraft instruments back in the day would remember screws that had "hex spline" heads. These were basically a six sided spoked kind of pattern. They were commonly used on the little knobs that adjusted (whatever) on the gauges. The big problem with these was that the tools would strip with just a thought at times. Torx ended up as a kind of cross between hex spline (there were 4_spline and 5_spline, too) and what's commonly called an Allen hex head. The big advantage to Torx (over hex Allen) is that there is substantially more surface contact between the tool and the fastener (as Raiyn alluded to). It's the same as when you hear "the distance between Oregon and Mexico is 400 miles, but the California coastline is actually 2500 miles long". I'm just guessing at those numbers, but we've all hear those kind of stats and said "huh?".

If Torx fasteners are not overtorqued when installed, you should never have a problem with stripping the heads. Yet one more reason that most people should use a torque wrench. The two major causes of fasteners getting stuck are overtorquing and not lubricating the threads. You see it hammered home almost daily on this forum. You need to grease (or use anti-seize paste) just about every fastener and mating surface on a bike. If you don't, expect problems down the road.

Another thing that a lot of people seem to miss is that if you Loctite something and it gives you a difficult time coming out, take the time to heat it up for a couple of minutes with a hair dryer or heat gun. Alternatively, there are release agents available for threadlockers, but they are nasty chemicals and heat works just as well. This will save you a lot of stripped tools and fastener heads. For people that don't have a lot of experience with using Loctite, it's very important that you match the strength of the Loctite to the size of the fastener. If you put 270 on a 4/40 or 2mm screw, that is no good. If you did not understand that last sentence, then you need to either seek advice when using threadlockers or spend the time to learn what threadlockers match what fasteners and applications. It's ain't rocket science, but you have to take the time to learn the correct matches and applications for this stuff. If you get it wrong, plan on plenty of stripped fastener heads and tool bits (and the accompanying frustrations).

Sorry about the tangents, but alot of this stuff is related. Experience mechanics can often get away without the torque tools, but a good example of why you should use them is stated in Gerd Schraner's book. He states that after years of building wheels with no tensiometer, he was surprised at how inconsistent his own work was when later checked with a calibrated tool. Anyone who does not use torque tools, and starts to, will find out the same thing.