If by "suitable" you mean for a particular purpose (Schutzhund, or other competitive sport, SAR, or as a family companion), that would cover basic temperament, but not necessarily personality. Unless you're an expert on structure, which most people aren't, I would rely on the breeder's input there, and all things being roughly equal - nerves and drive, gender, and structure, I'd go with personality and looks to make my decision, which are subjective.
As Patti mentioned, calm is good. You may want a more aloof dog, or you may want a more social dog. You may prefer independent dogs, or you may love snuggly cuddle bugs. You may want less prey drive if you have a small dog or cats, or you might want a dog that goes crazy for balls and other moving objects, a spitfire or a more laid back dog. That's all personal preference, and much of that is apparent at a fairly young age. For example, Keefer was described by the breeder as being affectionate, outgoing, and first to the food bowl among his litter. She was absolutely dead on! He thrives on physical affection, is confident and social with people and other dogs, and will do back flips for food. Dena was chasing and retrieving balls that she could barely fit in her mouth at 9 weeks old. So that's the kind of thing I'd want to know about their personalities.
And lastly, there is nothing wrong with preferring certain looks. Sables, solid blacks, bi-colors, longcoats (my fav), go with whatever grabs you. I'd assume that even if you wouldn't be able to meet the puppies in advance you'd at least get to see pictures and maybe even videos, which would be especially good because you could see them interact with each other and their littermates.