First , and foremonst this comparison is observations on my part, and just my opinion. It does not mean that every TT or Havanese will exhibit these differences or similarites.
Tibetan Terriers are affectionately called TT's, and are not terriers. They do not have any characteristics of a terrier.
They are friendly, and usually get along well with other dogs, people, and children.
They are mischeivous as puppies, left to their own devices , they will find their own"fun", which may include chewing your shoes , to checking out the wires on your computer!
They like rountine -- and schedules. They find crating as a home of their own, and feel content .
They make a great companions, but do not need to be the center of attention. They were bred to accompany the Tibets on journeys over the treachourus mountains. So they are very sure footed and agile, and think on there own.
They are very clean, like to have a special potty area, which makes them easily house trained.
They will bark at strangers when they come into the home, then are content to watch from a distance.
They are very aware of their enviroment: if you get a new chair, or put a new ornament in the garden they will approach it as a stranger in their domain.
They are very smart but do not take to traditional training, they need to think it was their idea ! They respond well to clicker traning or treat training.
They need groomiing, can be kept in a puppy clip, are generally ok with allergic people. But my opinion on this is to meet the particular breed which you are interested no matter what the breed, to see if the individual would react to the dog
Tibetan Terriers are known as the GOOD LUCK dog.
The Havanese are in the toy group. They are energetic, happy, curious, smart.
They are easily trained, love to please. respond well to both clicker, treat, and mild traditional training.
They are small, between 10-18 lbs., and from 81/2 to 11/1/2 inches at the shoulder.
They can be crate trained, but do prefer being with you, so much that it can become annoying (as one owner put it). Separation anxiety.
They are not easily housetrained, like most toy breeds, altho there is exceptions to the rule. Some girls will have dominant marking habits.
They do not tend to chew or be destructive (except paper fetish).
They are easy to transport (if crate trained) ,underseat of plane,etc.
They need grooming, can be kept in a puppy clip, again are generally ok with allergic people. Same as above
Let me repeat myself , and say these are just some of the observations I have observed in raising both Havanese and Tibetan Terriers.