IME, Mals are different. They are more "operant" dogs and super quick. They think less and react more. This can be good or bad, depending on your ability and timing as a trainer. If you are as quick as the dog and are able to stay ahead of the dog mechanically, then they can be a blast and super flashy!
If your experience level is lower and you still struggle with the mechanics of training, a Mal may learn lots of bad habits and end up being difficult for you. They also get frustrated easily if your communication and timing are off. Don't get me wrong, there are GSDs out there that are pretty quick, but they tend to be more forgiving of a novice trainer.
Dogs are all individuals. I would spend some time with the parents of the litter if available and see what they are like off the field. A solid Mal with no nerve issues and an off switch can be a load of fun to train and work. The same can be said for a good GSD. They are just different in how they work.
I'm not trying to discourage you at all. I enjoy training Mals as they usually have the drive necessary to do many reps of the same behavior and not get bored, especially when mature. You can move pretty quick with a Mal on positions and detection because they will put up with a lot to get their toy. At the end of the day, I would rather hang out with a GSD because they are more about the relationship with the handler and less about getting to the toy. The tightly bonded relationship and individual partnership can be found more prevalently in the GSD. Most Mals will work for anybody as long as the toy is there IME.
As a disclaimer, YMMV. I have met some very Mal like GSDs, and some very GSD like Mals. IMHO, a good dog (for the individual handler) is a good dog, regardless of breed. I think there is no "Dark Side" in the world of working dogs
There are also some great Shepinois (GSDxMal) dogs out there!