Chihuahua owner here,
Cons
Nightmare to housetrain! I have two my mums has 3 and anyone else I've know has had the same problem. Especially when raining!
They do like to bark - chihuahuas are ranch dogs in Mexico so are bred to chase off larger animals - they are usually in a pack
You can't have just one - I find they do better in multiples
Pros
Very loving - they love to be on laps, as soon as anyone sits down they are on your lap.
Big personality - tiny dogs with big personalities one of mine loves to dress up - gets super excited when he sees a jumper or a costume and will put his own head in the outfit.
They can walk for hours or go without - I find they aren't bothered or going to tear your house up if it's horrid weather or you are sick and can't get them out for a walk where as other breeds really do need to get out everyday.
Excellent family pets - all the chihuahuas I know have been brilliant with children especially my ASD daughter.
Cost - daily costs are low compared to many breeds, food bills are lower, no need for groomers, apart from luxating Patella issues health issues are very low compared to some breeds.
They do like to shiver but this could be cold or excitement.
I would recommend this breed every time but if getting a puppy classes are a must! They can be very headstrong and need to be socialised properly to reduce the barking while out walking.