You are so in luck, I have one of each, well the GSD is mixed with blue heeler so it's not like she is any lower in the energy category. LOL
Since you got lots of good stuff on the GSD I'll fill in the blanks on the Mals.....
While they are a lot alike they are also very different, how I describe a Mal to people who don't know what they are, is that you take a GSD, toss it in the dryer to shrink it some, give it 3 shots of espresso and let it loose. They aren't high strung, but they are high energy and can have a very high prey drive. They need lots of training and a job, now the job can be as simple as picking up things on the floor but they need to have a job. If you ask one to do something it is more than willing to hurt itself to accomplish the task.
They tend to not be barkers and when they do bark it's something worth barking at, they take their job as protector very seriously, so you have to socialize them tons with all kinds of people. What is interesting is every Mal I know LOVES kids and is wary of strange adults (not aggressive just watchful). I can't keep Sherpa away from the neighbor kids yet he will avoid letting a stranger pet him.
They are super versatile, Sherpa does water retrieving, agility, obedience, "therapy dog" activities like retrieving my purse by name, tricks, and anything else I can come up with to work his brain. An average day for him is a 5 mile run, 30 minutes of formal obedience, and 15-20 min of fun stuff like the retrieving or tricks.
I live in an apartment, but as you can see we do plenty to keep him busy, the thing is if his brain isn't kept busy he finds way to learn new things he shouldn't like how to push the pedal on the trash can to lift the lid.
They are lean strong dogs with very few genetic problems because they have not caught on with the back yard breeders like the GSD has, but I know it is just a matter of time.
This is one breed along with the Dutch Shepherd (almost the same dog just different colored fur) that I would never recommed to people. I have had Sherpa 8 months and it feels like 10 years, he was a rescue and the 1st 3 months almost killed me (oh him one of us was going to die) while we were training him and working him to learn non-distructive ways to express his energy. So do your research and if you are ready for the challenge, you will discover a breed that will give back to you 10x what you put in.
Here is a great website that really discribes this breed well. http://www.malinut.com