There's no way to determine that unless they actually joined up, which sadly, will never see the light of day, despite all the fancy talk.
It's been shown that anyone can beat anyone on the day in the Premier league, Burnley have beaten United, ourselves and other big names at turf moor, you never know what is going to happen.
and Rangers and Celtic have both reached European finals in the last seven years, Parkhead is a testing trip for any team in Europe, and a partizan crowd really gives them a 12th man, I do think they need to play ouitside of the SPL, It's just not going to happen any time soon thats all.