Recommendations on dog breeds? (long)

I'd look for a dog that has been in a foster home long enough to be well evaluated for cats and wouldn't worry about breed. For example my 60 lb Golden Retriever/Chow would fit all of your requirements nicely. She's lived with cats since puppyhood and just doesn't consider them to be prey. Instead focus on finding the right rescue organization. One that really, really screens the dogs and matches them with the right home.
 
I think you are wise to choose a mature dog. Our last adoption was a four year old Malinois and we didn't miss the frustration and destruction of a youngster one bit. He's also the most affectionate of our three dogs--perhaps he knows how good life is.

No Tollers, they are quite active. I can't imagine one fitting in with the schedule of a busy vet's lifestyle. I can definitely visualize a rescue grey there! Maybe two or six, lol.

I do assume you'd not make a snap decision whether you are waiting to provide a home for the right dog, or not - either way you will have to find some way to steel yourself against those dogs that will need homes. And you will even have to put down perfectly nice dogs because they can't find homes, and you can't give out medical care for free to every pet that needs it - so either way you'll have to find that line somewhere, and know it's not your fault that the line has to be drawn.

My landlord's daughter is in the same place you are - she's desperate for a dog (she wants a Border Collie), but she just started vet school in fact, and knows it wouldn't be fair to an active dog. She's going to wait and see what life sends her way, as she already works at a vet clinic and knows what it's like.

My own vet, on the other hand, had a household of Berners she bred herself and never adopted a personal dog from her clinic. The clinic had a couple "mascots". She was an animal control officer before she got her vet cert and I guess she learned to close her heart, so to speak, from that experience.

I also never adopted any of my fosters (um, except Zhi the Chinese crested), or any dog from our rescue. It's not that I was never open to the possibility - I just always found better homes for the dogs, than my own! My own requirements were very tough and even well-bred dogs rarely tempted me. I rarely, however, have to face the option of "keep the dog, or put the dog down." Although one of my current fosters is on the verge of that category - we are still evaluating the situation.

do you like bassetts? total couch potatoes, friendly to everyone. I think most of the breeds you list (shelties, poodles, cockers) might require more exercise than you are willing to put in. But really, any rescue is likely to have a mixed-breed dog that meets your requirements, just apply and say the same things you posted here and see what they come up with.

I think any dog low in prey drive will get along best with cats.  My Greater Swiss will allow my cat to rub, purr and sleep on him.  But...  if the cat is friskey and decides to make a run for it in front of my Swissy - his prey drive kicks in and off he goes into a full blown chase, up my couch and over my chairs!!  But they are kind to each other for sure.
 
How about Pugs? My pug is great with my cats.  My former mixed breed, Gordon Setter mix was very good with my cats too. 
 
I also think if you get a dog as a pup, they will grow up being accustomed to your cats.  If you get and older dog, they will already have to have been exposed.
 
Good luck!!

I think the best way to get to know the breeds is to be around them.  I'm sure during your schooling you will have to work with many breeds and once you start your practice you will see many more.  You could visit shelters/fosters and ask to see their dogs.  Take your time and get to know them.  Also to get a good idea of breed specific characteristics you can go to dog shows, talk to the handlers and ask about the dogs you have in mind, many are happy to talk about their breed.  For the most part just get to know as many dogs as you can, I personally find it very fun doing this.

Everyone has given such great advice.  I love it when the forum comes together and talks about the dogs that they've owned and loved and their remarkable personalities.
 
To the OP:  I would stay away from most sighthounds with the exception of Greyhounds-some of them are so calm and chilled out even with the most irksome cats they'll just walk away.  I would also stay away from most of the retrievers as well-they seem to have a constant need to do something. 
 
Adopting an older dog is a great idea. I actually think a mixed breed would probably suit you just as well as any purebred. 
 
I wish you good luck in finding your lifelong companion.

Both Shelties that I've known in life were both great with kids and other animals.  My sister's lived with another dog  and  FIVE cats and never a problem.  He passed away at age 14, but he was a nice dog.  A little "barky" sometimes, but then again I think all dogs are barky compared to mine that rarely barks! []
 
Good luck on your new career and finding the right older dog.  I too would be afraid I'd want to bring all the dogs needing homes home with me!

I think a lot of these breed descriptions we read are gross generalizations. A breed will tell you a lot about your dog's predisposition, but from what I've seen so far, (dogs in our family, friends) it's personality first, then breed. (One of my fathers' German Shepherds was so hard to protection train... despite all the effort! He'd rather help thieves carry things out of the house than protect.)

It will be just as important for you to pick out the right puppy out of the litter as it will be finding a good match in terms of breed.

PS. What about Basset Hound? In general low energy dogs, good with cats, might take off without a leash, might drool a lot, very very cute.