I would prefer the 6200 model myself. In all honesty- I feel that the 7300 and 7400 models were less reliable - and more non-user friendly than the old 6200's. Not that they arent a good HU, its just that they kept the same basic features and just made them harder to get to. Not to mention the general case deisign of the 6200 differs slightly from the newer models. It sat closer to the main unit itself- while the newer ones tend to float out away from the unit.
I have seen a good number of the 300 and 400 series decks in for repair due to the face breaking loose, while I cant even remember many of the old 200 series having problems with much at all.
I used to run a DEH-P7200 (yes- dolphins! //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif ) and always had great luck with it. If I could locate another one that is New -In box (not refurbished) - then the chances of making it my full time HU as a permanent position would be likely.
take it easy,
-zane