I have 3. Two girls who are sisters age 6 and 1 boy age 4.
Very very clever, very loving. Yes they are more vocal but can be trained to keep it to a minimum.
Mine are pigs, food rewards, positive talk, belly rubs do it every time for whatever you need to train them for!
The boy is more cuddly but I prefer girls, they have been much easier.
The boy is tiny, far more energy, rarely sleeps in the day. The girls are happy to snooze a lot.
All have health issues. 2 with multiple allergies both food and environmental. One with luxating patellas even though its parents were free of it!
The boy is much, much harder work than the girls. In hindsight I would have not got him even though he's lovely in his own way.
They're all very unique personality wise. They're all attention seeker's and demand affection all the time. It's not a breed who is happy to have a walk then go lie down in a corner the rest of the day. Chihuahuas tend to follow you about and want to sit on you or next to you most of the time.
I love them despite the few downsides, they're so comical, so loving and so smart. I can't imagine having any other breed. I've had others in the past but chihuahuas are the best for me and my lifestyle.