As cars get older their decline in value reduces and reaches a break even point, R32s have pretty much hit this being over 20 years old now, even R33s will be hitting this point soon. The fact is R33's can be over 15 years old now so it is at the point where a well looked after R32 is just as likely to be reliable as an R33. R32s tend to be more 'enthusiast' oriented as well, and from what I can see are usually less showy and more to the point, probably a lot more suited to the track/weekend car market than a R33/R34 is. In a lot of peoples eyes they are a lot more desirable.
I'm biased because I have an R32 for sale for $8000, but it is quite well modified, and I would assume much more reliable than any $4000 R33, and a much better basis for a track car. I've rationalised this by looking at the market and then adding about a 1/3 of the cost of all the modifications I have done(since they have all been done recently). I currently have someone waiting on money to buy mine because they want a good street/track car, I've had other people come check it out and not be interested because of usual old car problems such a few scratches and paint chips and expectations that you would have for a normal car that just aren't realistic and should probably just go buy an R33/34 if they are worried about that stuff.