Ive lived both places. I find that while Minnedosa is pretty, its a really hard place to fit in. There is the lake, but really not much else other then the ski hill. The highway between Minnedosa and Souris is always crazy, so if you go into the city its the one road and thats it.
Souris while Ive heard its cliquey, People acknowlege you here. They smile and will chat. The waterpark is here for the kids, the cost of living is still reasonable. The city is 25 minutes away and you have two highways to get there.
Not alot for businesses though. So depending on your lifestyle you may have to drive to Brandon for what you seek.
Ultimately everyone has a differing opinion. You have to find your own niche. Good Luck