RE: Roto start or Pull start
For Break-in, a roto-start is great.
For cold weather, a roto-start is great.
For a poorly tuned or otherwise finickity engine to start, a roto-start is great.
So, if you have a reliable broken-in engine and live in a warm climate, a pull-start is fine.
Keep in mind, in cold weather you have a jacket on with pockets for your roto-start, glow-driver, etc. In warm weather, it may be a bit inconvenient to carry that stuff to your bash or race spot.
Roto-start batteries will usually last at least the duration of your day of bashing, but if they don't, it's not much different than having a pull-start string break. Either way, the day is over.
One last thing....with many vehicles, a roto-start will allow you to start the engine without removing the body. Installing a body with the engine running finds you starting to drive with your fuel level already lower than full. This seems to be more of a concern with 1/10th on-road cars than MTs due to the smaller fuel tank. It's a quick re-start to if you stall a cold engine....no need to remove the body to get to the pull-start.