I don't check out this forum very frequently, so sorry for a slow response.
I've owned several LMs, the first one around 1980. Obviously I like the breed.
I have not owned a SM, but have watched them work at Navhda tests.
You may have learned, that despite their names, they are not related breeds and developed independently. LMs are a bit bigger according to their standards. LMs are strictly black and/or white (their "sister breed" is actually the German Longhaired Pointer, from which they separated, creating two breeds, strictly over the issue of color! GLPs are brown or brown/white.)
Both Small and Large Munsters are "versatile" breeds and hunt upland, point, retrieve, and hunt waterfowl and furred game. I'd say that SMs are a little more active and quick moving, but both are athletic.
They both sport long, thick hair, which is great for warmth and looks, but can be a challenge for burrs.
I believe there may be two SM organizations, while just one LM organization in the US (and one in Canada.)
What I like about the LM, which keeps me sticking with them, is the their organization's strong commitment to breeding standards. No pups are placed in non-hunting homes (in theory) and no breedings are to take place unless the LMAA (the association) approves the breeding and the parents have passed hunting tests and met physical standards. In general the LM (which I know best) produces healthy dogs that live long lives and are good hunters and companions. My last female hunted through her 15th year and we put her down at 16 when old age made her back legs and bowel control give out, but she was still healthy otherwise. I've seen others live up to 18. Of course, with EVERY breed there is a wide spectrum. But on average LMs are dogs with good temperments and good noses. They don't have some of the traits some hunters desire when they hunt pointers, setters, or spaniels, for example. I would say most LMs have shorter range than pointers, though my current males is always pushing the limits! The generally excel after the shot, at tracking and retrieving, compared to other upland dogs.
Perhaps my other favorite breed, again, because of some pretty good breeding control in some circles, is the Pudelpointer. But that's another topic.
There are good dogs from every breed, and crappy dogs from every breed. However, the odds of getting a good one (health, temperment, ability, etc) is far greater in some breeds than others, in my opinion. I want a pup from parents (not just grandparents) who have some hunting test qualifications, who are at least a couple years old (so enough time has passed to see there personalities, if they are aggressive, etc) and I want someone qualified to have looked at the genetics and deemed it a good match. Life is too short.
Feel free to message with questions. However, the only way to get one is to watch the LMAA website and contact the breeders.
http://www.largemunsterlander.org/Photo is of my current pooch pointing a sparrow on a spring walk.