This is normally a big no no but I have the best of both worlds, I have a Yorkie, Chiuahuah mix
I've seen chiuahuah's that are grumpy and crotchety, but then on the other hand, I've seen some that are SO outgoing and just love everyone. I think their temperament has a lot to do with how they're raised and socialized. I'd spend time with both the breeds before you make a choice on which breed is right for you. Good luck.