Disneyland Hotel Pool: Has the very fun Peter Pan theme, a 100 ft long slide, a smaller, kiddie friendly slide, lots of nice landscaping that includes palm trees, grass and sand areas for the kids to play in. At the quiet pool there is more sand as well. The main pool has a very large hottub and kiddie pool. They have a pool bar where you can order a drink and Crocs Bits N Bites where you can order burgers, nachos etc., for food options. Both the snack and drink bars are get it yourself, no waiters come around to take your orders and bring them to you.
Paradise Pier Pool: Basic, square pool but a really incredible slide. Totally amazing a kids and adults slide extravaganza! The slide does not exit into the pool which is nice if you have a kid that is not a strong swimmer since it doesn't let out into a deeper end but rather just a maybe one foot deep type thing. Paradise Pier does have a pool bar, it was not open for either of our stays in September. So maybe that is more of a seasonal thing. It has some chairs and a shaded off area but no landscaping to speak of. Its on about a thrid floor rooftop area and does have a nice view of the fireworks at Disneyland.
Grand Californian Pool: Redwood theme, very cool slide. Has two (or even three maybe?) different pool areas, separate but yet connected, a kiddie pool and a nice hottub. Whitewater Snacks is right there and has wonderful food, burgers, sandwiches, nachos etc. They also have a pool bar. There is a waitstaff that circulates to take food and drink orders, or you can handle that yourself to save the tip. You can see some of the California Adventure attractions like the Sun Wheel from this pool area. It doesn't have the landscaping the DLH pool does but its a very nice pool area.
As for offsite motels, probably the nicest pool area is the one at the Howard Johnons. They have a main pool with a hottub, kiddie pool and spray jet area that is very nice as well as a separate quiet pool. There is no slide. From the hottub area in the main pool, you have a nice view of the fireworks. The other offsite places I have stayed have just had your basic, small, square pool. Almost all of the motels near DL are older, built before motels put in these modern day pools you see today. But they are still nice places to hang out for a swim and relaxation time.