From what you said, you've hit on the big area of the 91 that is of more benefit. If you're in hawaii, you will be using the A/C a lot. The 91 system is similar to GM and FOrd, and as such, is easier to work on and personally I find it more effective.

There are a FEW people who have done killer conversions to 134a refrigerant in their 90 and earlier cars, though. The big thing here is if you are going to do the work, or foot the bill. Since it's already converted, you'd save big on work to that A/C system.

Also, the 91 has optional ABS brakes, which are nice. Most don't have it, but there are some out there that do. Check and see if that one has ABS. It would be a nice feature. Either way, the 91 is a year newer so it makes sense that it would have a few more miles.

It has always been my experience that the Volvo with a few more miles is the better one, and certainly in this case the '91 would be the better choice. A/C systems that still use R-12 refrigerant are more likely to break down, not to mention that R-12 is the equivalent of liquid gold in terms of pricing and availability. What also would get me on the '91 is that considering the owner put up the money for the A/c upgrade and the CD player, he/she is more likely to have gone the extra mile in terms of other service issues on the vehicle as well. Good luck either way!!!

Richard.