I have the Taser C2. A good friend has the M26.
The C2 is a quality product, and well engineered. It is small and light enough to carry around in a jacket or pants pocket, which is great.
The registration process was no big deal. The instruction DVD was a good training tool. The laser aiming system works well, and should intimidate a lot of would be attackers. The flashlight led is very useful, too.
I have not used it in an actual self defense incident. A sheriff buddy of mine says he has seen some Taser rounds misfire and go off in wild directions.
Forget about reloading during an attack.
The rounds are $25 a shot! You have to buy a special Taser battery pack, too, every 2-3 years.
You can use the C2 as a stun gun, too, but it is far less effective.
The 15 foot range is decent.
The M26 is too big to carry IMHO, especially in its holster. It sticks WAY out. Maybe if you live in Alaska and you wear lots of layers you could get away with it. It really has a gun look, especially when it's in it's holster, which may be good or bad for you.
Also, on the M26, the safety can be moved while you carry it. This activates the Tasers electronics, and the batteries can become drained without you even knowing it.
I think OC is a better choice because you can engage multiple targets, it has a longer lasting effect, and it's a lot cheaper!