Its a very good question from Cory. Curry King hit the nail on the head..
The 100 best balti book which is supposed to be from genuine balti houses has given me results which are average at best and if that is "proper" balti then it's not for me Dont like 100 BBB
The main differences ive perceived: Balti isntt originally Bangladeshi but probably Pakistani in origin. The spicing is different, using more aromatic spices. Although the spicing ive seen from Pakistani recipes has been very basic. So it might have started as a gimmick..as it doesnt fit the Pakistani spicing ive seen or read about on the interweb. Pat Chapman believed it to be from Baltistan.. sounds too incredible? Only problem there is in Baltistan they slow cook there dishes.. not wokfry them.
The Balti dish isnt any quicker than a normal BIR, probably takes about the same time to cook or slightly longer.
The Balti will taste different, it relies more on fresh Coriander, Methi, has a different garam masala, more cardamons and cloves. More aromatic spices.
The original curries of the 1970s were very hot (apparently) where balti was a reverse trend, making a "sweeter" milder version. but the other major differences is that it was very much a mix and match type of curry. Where as the standard BIR dishes were mostly "meat" in a spicy sauce, Balti can include a combination of onions peppers gourds pulses and lentils lamb and chicken or "meat" and prawns within the same dish.. closer to a spicy stew i guess, which is cooked in a large kari on the stove and severed in the same Kari or Balti bowl
Yes the "Balti triangle" is pretty run down area... i know i lived not far away, and some of the places had glass tops with menus under (some still do..) think thats cool tbh.
although the ambience was a little dodgy with the strip-lighting and bolted down seats.
Another gimmick was that the nans were huge but werent included, they were ordered seperately and no knives and forks were included either. These places werent usually licenced either..(very cheap) there was usually an off-licence near by, and you could happily turn up and the Balti place would provide glasses or open bottles as needed.
After saying that, ironically there seems to have been a move over to the more traditional "meat" chicken/prawn dish in just a mild spicy sauce closer to the BIR.
Indian restaurants also have done their take on the Balti.. which is also very good but the distinctions become less apparent.
Just want to say one more thing, there are some "traditional" Balti places around but not all places are great or even good. Much like the BIR, there are some places which just arent up to scratch.
Conclusion; Balti isnt a million miles away from your local BIR but it could be just far enough to be different

Regards Ashes