Hmmmmm....Tough question to answer without knowing your criteria and what you look for in a hotel. None of them are exactly cheap. If you are on a budget, I probably wouldn't recommend staying at any of the Disney hotels. If you're dead set on staying at a Disney hotel though, don't expect the same kind of immersive experience you'd get at WDW, unless you choose Grand Californian. Unfortunately, that one's the priciest of the three. As Disney hotels go, it is unquestionably the most convenient, even more so than any at WDW. This is because DTD is just outside the entrance, and both theme parks are just a short walk. It's also quite nice, although I didn't find it as elaborately themed as a lot of people claim. It's definitely more elaborately themed than DL Hotel and Paradise Pier Hotel (which are basically not themed at all). So I suppose by comparison, it SEEMS elaborately themed. But I guess I'm spoiled by the great themeing of the ones in WDW.
If it were me, I'd probably go one end of the spectrum or another...I would either spring for the luxury and convenience of the Grand Californian, or I would stay at a clean, but cheap non-Disney hotel nearby. I wouldn't personally stay at Paradise Pier or DL Hotel again. They're both overpriced for what you get, in my opinion.
If, after all this, you still are set on staying at one of those two, I'd recommend Paradise Pier over DL Hotel. It has a much newer, fresher and cleaner "feel" to it than the DL Hotel. As an earlier poster said, the DL Hotel does seem a bit "run down".
