maski: All right heres the run down.
-The only real weak point on the car is the hinge pins. The fact is that this is a neccesary evil. When you hit something, SOMETHING HAS to give way. On this car its the hinge pins. A peice of advice though, the hardened pins aren't really any better than the light weight ones, so stick with the light weight units.
-The difference between the C4 and C4.1 is huge. First the C4 AGLE has a longer wheelbase than the C4, and the C4.1 wheelbase is even longer than the C4 AGLE! Both cars use graphite chassis, but the C4.1 uses the flake style graphite that we usually associate with the "graphite" look. Of course the battery layout is different and the bulkheads are different. The new bulkheads lower the diff and its outdrives slightly to keep the universals at level.
-Well if you're getting an original C4, I would say pick up the C4.1 upgrade. It turns ANY version of the C4 into the C4.1. It goes for $149.00, $30 cheaper than it was originally. For what you get, its a great deal. You get a whole new chassis(upper and lower), all new black anodized bulkheads, new battery holders, new shocktowers and body mount, and a new front belt. And any hardware you need to make the transformation. After that I would suggest looking at the transponder mount, new "full round" axles, and some would suggest the front one-way diff.
-I would give it a slight edge over the Pro2 in durability. Why? Because the C4.1 doesn't have king pins. Any car with king pins is prone to bending them. So thats about the only thing I have noticed that was different between my C4.1 and my buddy's Pro2 in durability.
You could also surf the buy and sell forum here or the one on www.hobbytalk.com
and see if you can find a used C4.1, instead of buying the C4 and upgrading. Either way, you can't go wrong with a Corally!