I'd actually recommend one used over a normal Caprice because you can usually get them as a bargain (same goes as ex-taxis). Do be aware, though, that it's very different from a regular model - plastic rear seats, unopenable rear doors, and there's sometimes a cage between the front and rear, even on 'detective' models.
Only get a used Caprice - it's just a waste on a used Crown Vic, considering they're cheap enough used without having to get a high-mileage ex-cop version.
Nevertheless, if you were really interested in rear-drive large sedans, I'd recommend a 94-96 Impala SS over anything...