Until two pups meet and spend time together, who are we as mere humans to say who will have chemistry or who will not. However, when you are looking to find your pup's new best friend, you might consider the following:
Size!In general, dogs of similar size and weight might be a better match for a couple of reasons. First, you won't have the Napoleon Complex (I'm smaller therefore I will overpower you with my aggressiveness, attitude and fierce growles) or the 'I'm going to get the crap beat out of me' fear factor that some small pooches have, and for good reason, probably some sort of innate survival instinct. Second, a great size difference increases the risks of the little one getting hurt, even by accident.
Breed, or is it temperament?
It's mostly temperament, but it could be a specific breed whose temperament is so hard wired and inbred that even its own rearing and
environment can not change these behaviors (don't be sad, this could be good or bad). I love this resource at Dogtime.com, breed characteristics. Check out what breeds your pup might be a match with.
Age.It is not age per se that determines a successful relationship, but rather interests, energy, drive and patience to pursue those interests. Ask yourself, what would my pup do on a Friday night--hit up a night club and dance until his/her knees buckle or stay home chill on the couch watching an oldie but goodie, movie? Perhaps, a combination of both. Age kinda does matter for a long lasting relationship.
Sex.Personally and anecdotally there does not seem to be any rhyme or reason why pups of the same sex will or won't get along. I know there is research that support same sex aggression (mostly in males), but I have not in five years as a full time in-home pet sitter having watched many (MANY!) dogs experienced a trend. However, if your dogs are spayed or neutered, well-trained and properly socialized, then sex may be less of a factor (if at all).
Sign-up for a Pup Mixer and lets see what is fact and what is over-generalizaitons when it comes to what pups are compatible.