[cj847]

I installed vintage air in my 71. I installed Old Air in my 67. The vintage air has significantly better cooling (especially this summer). VA has a bigger evaporator, so I am not imagining this difference. You Must tint windows to be happy with old air.

Vintage air - uses up most of the glove box space. It requires more sub assy than Old Air. The "sure fit" system comes with complete hoses, just be sure you have a complete description of your engine.

Old Air - salvages most of the glove box. It has a variable thermostat on the evaporator. I think the gen II vintage air has one as well, but I am assuming you are going gen IV. The old air was easier for me to install working by myself. OA "sure fit system" comes with hoses terminated on one end. You have to cut to length, mark orientation, and have the A/C shop crimp them.

I think (not sure) that the ECU you are referring to controls the cooling. So, the gen IV is less likely to freeze up due to wrong thermostat setting.

I think (no experience) that the classic air unit is a copy of vintage air.
Another that you didn't mention - no experience with Resto-mod air

I would go VA for sure. The old air is perfect for a small street rod where space is at a premium, but our trucks have the space. For someone with a Suburban, Old Air makes a nice rear air unit.