I grew up with Gsd's and have been owned by a couple Rotti's. I am currently owned by an incredible Gsd, Nando!
My opinion is they both are incredible working breeds. A dog with a good temperment is of most important no matter which breed. You can find crackpots in both breeds....just like people. I find them to be very similar. Both breeds are very loyal and extremely family oriented. Very intelligent, strong minded and need training, training and some more training (this is mostly for us!
) Niethier my Gsd or rotti's lend themselves to strangers easily....no agression, you can pet and greet them just fine, but they could really careless about outsiders. This has been my experience. Good luck, If your going for looks a beautiful Rotti takes my breath away.
My Gsd is definitly a looker too!!!!!!! LOL!
Personally I don't think you could go wrong with eithier!