I do a lot of HVAC work and have dealt with it all my life. You can't really determine the unit size based on square footage. It depends on too many factors. Quality and type of insulation, type of walls, occupancy at peak times, etc etc etc.

My previous bar was a very old building with poor insulating materials and we had 1750 square feet. Thursday thru Saturday nights we averaged around 250 at full occupancy (170 fire marshall rating). Two 5 ton units couldn't handle it in the summer.

You aren't going to believe this but I currently have 4900 square feet at our current bar and we have a 3 ton unit handling it fine for both winter and summer. Difference is that both sides and the back of the building are mostly underground. It's like a cave in there and will stay at comfortable temps without any heat and air when empty. Seems like it stays in the low 60's year round in there even without the heat and air on.

I haven't dealt with the ductless units Pubboss but from the ones that I've seen they are powerful units for individual rooms but I'm not sure how well the air would circulate to the middle of the bar without ducting considering how many people you have in the place. With that many people the center may get much warmer.

By the way guys, I'm new to the site and hope to visit frequently to get advice and also help if I can.