Hi Susan,
A few things to throw into your mental hopper...
I think the first thing that is critical is to make sure you go for a breed that
really appeals to you a lot. You will be living with this dog for a long time, after all, and the majority of your time together won't be spent on your sport. So, the size, looks, and general temperament of the dog will be important, IMO.
Deciding which sport you want to pursue may make a difference for you, too. If you go the Schutzhund route, well, GSDs are king of it. They are bred with the kind of grips that are rewarded, and many clubs are very preferential towards the breed. Some clubs are more open-minded about working off breeds, so it's a good idea to find the club you want to work with and see what kind of variety they have in their club, breed-wise. If you went with a Mal, for example, and joined a club that doesn't have any experienced Mal people, well, you could find it on the frustrating side.
The ringsports tend to reward the lighter-framed dogs (Mals tend to rule here, and Dutch shepherds, to a lesser degree). The kind of grip that's rewarded is different than in SchH, which is reflected in the breeding tendencies. Their temperaments are definitely different from a GSD, which circles back to what your preference will be in living with and training your dog.
I think it's also important to consider how competitive you are. If doing well in competition matters to you, that will impact your decision. If you're more along the lines of just wanting to have fun and explore a new venue, then it won't matter as much which breed you choose.
I agree that with working lines, for a first-time owner, it may be easier to go the medium-drive route, but this is another area in which you really need to consider your own skills and preferences. The higher drive dogs, while a definite challenge to live with and keep happy, to me, are easier to train. They are
highly motivated.
Building drive and motivating a lower-drived dog can be a lot of work. So, you have to know which trade-offs you want to make in this regard (and it's not like you're inexperienced in dogs, so you should be able to do an honest self-assessment here).
Whichever breed you decide on, as I'm sure you know, there will always be a range of drive levels in litters, and depending on the lines you choose, you can also lean towards how sociable, easy to handle, and liveable your dog is likely to be. Doing your research here is critical.
There is no substitute for meeting the dogs...visit some clubs, check out the different breeds, see what really appeals to you.
Personally, I'm a sucker for the herding breeds.
I sure envy your proximity to ME's school! You also have a lot of protection sports options out there, in terms of clubs and such. Check out Mondio if you can.
leih