Hi Tim.
The first thing you will notice about the minor is how much easier it is to work on!!! You don't have to be a contortionist to change the spark plugs for example
In my experience The Beetle is an inferior vehicle (based on having owned 2, one a bit clapped out and one a show winner) and driving the minor is a far more pleasant experience. The big advantage the beetle has (certainly the later models) is disc brakes! Conversions are easily obtained for the minor though, either ital/marina based or Ford.
For £500 you should be able to find a structrually solid (which is the MOST important bit), but grotty looking car which will likely need some attention. As has been said, see if you can take someone with an experienced eye to go and have a look with you. Mechanical bits are cheap, plentiful and relatively easy to fit/replace and there is reasonable scope for tuning a minor, with 1275 engines, 5 speed gearbox conversions etc etc and if you are a bit more ambitious then its even possible to dump a zetec in!
As for reliability, it seemed to me that I was constantly having to fix little things on the Beetles (but that might have been the ex's driving style) whereas my minors have been relatively trouble free when sorted out. Sure, there are a few niggles but thats half the fun, doesn't stop you motoring and probabally less than a modern sub £1000 car.
The other thing you have to consider is running costs! All Minors (bar one) have free Tax and a lot of beetles dont, I seem to recall (maybe incorrectly) the beetles got high 20s MPG and minors return mid to high 30s (according to the GPS odometer, on a long, careful run I get 38mpg from Aggy!)
Of course, we are all biased on here, but why not try a Minor, enjoy a decent heater, and if it doesn't actually push your buttons then theres nothing stopping you from selling it on (afterall, they don't depreciate!) and getting another beetle.
