I think the teens (and the adults too) would prefer the Disneyland hotel, but I'm also a big fan of the Paradise Pier hotel (always received nice big rooms and great service here), so you really can't go wrong with either.
But, the Disneyland hotel has a faster pool slide (although smaller than the one at the Paradise Pier), the pool at the DL hotel has a great theme and is much larger. The hot tub at the DL hotel is VERY LARGE, plus the hotel also has a nice quiet pool. The grounds of the DL hotel are very pretty, with lots of folage, koi fish ponds, and waterfalls. The DL hotel is also more convenient to Downtown Disney, as well as the Downtown Disney Monorail station.
The rooms at both hotels are large and roomy (most of the rooms anyway), and although the rooms at the DL hotel may have a few extra Mickey touches, I actually prefer the decor of the rooms at the Paradise Pier. (That's just me though. Some prefer the room decor at the Disneyland Hotel.)
Both hotels have decent arcades, but if the kids are old enough to go out on their own a bit, the Disneyland Hotel is practically next door to the ESPN Zone. (The Paradise Pier hotel is about a five minute walk, but a safe walk, from the ESPN Zone.)
As I said, both hotels are great, but if you can, try to get both families in at the Disneyland Hotel. But if you can't, and instead can get both families in at the Paradise Pier, don't be disappointed because it's a great hotel too (plus you can watch the fireworks from the Paradise Pier pool deck where they pipe in the music/narration).
Hope everyone has a magical time!
