Having not been to any of them, I can't say from personal experience. But, having read a number of reviews, I'd say Shorty's 32 gets the most consistent praise.
I ate at Shorty's .32 a couple of weeks ago. Things we ate:
Short Rib w/ Mac & Cheese--excellent short rib, M&C could have been sharper (but I almost always think that).
Burger--great flavor, good bun, we ordered medium rare and it came out pretty rare which was okay because the meat was very good. fries were unremarkable.
Chicken--it was a quarter (or so) chicken and it was delicious. salty and crisp on the outside, juicy on the inside. came with haricots verts (I think).
All of the food was really good. We went late-ish (9:30) on a Thursday night and it was full but not crowded. I'd definitely go back.
Haven't been to Belcourt or Back Forty.
I too ate at Shorty's recently...about 3 weeks ago on a saturday night...pitched up early when it opened about 5.30...small room...not terribly inspiring decor wise...looks kinda cheap and cheerful. Ordered the burger which is getting a LOT of hype...came with blue cheese...was definitely substantial, juicy, plenty of flavor. Good deal for 14 bucks and fits into the gourmet burger category for sure. I also agree fries were average. Anyway, about 30 mins after I arrived the place was jammed and the table next to me were perusing the menu for about 20 mins wondering what to order...they too plumped for the burger but the waiter told them they had totally sold out of the burger...all gone within 40 minutes of opening!! He explained that since Time out had reviewed their burger highly it had been crazy on the burger front. Evryone in the room munching on the burger and by then it was only like 6.30...:) I will be back to check out the rest of the menu which looked good in a comfort food way and perfect for cold weather.
Gotta go with Shorty's 32...I've been a few times and it is consistently good. The burger is great, but so are a lot of other items on the menu, I would try the pork belly and crabsticks for apps and the short ribs for main. Enjoy!
My esteemed comrade had such a poor experience at BELCOURT that it has not even been spoken about.
Same individual said Back 40 was OK. Nothing special, not bad.
Personally, I have been to none but I would actually consider Shorty's .32 even without the above mentions.
Just another line of reasoning, leading you to the same choice.