Been a long time since I went to WDW, but based on what I remember and compared to what I saw at Anaheim last year my (incomplete) list of things that stand out or are quite different in DLP are:
- Dreams - night time show at park closing time in
Disneyland park. Not to be missed, on par with World of Color at DCA (and I liked it better than Fantasmic)!
- Incredible theming in Disneyland - it's just wonderfully themed, and the castle is amazing. And has a dragon!
- Unique shows/rides/etc in DLP: Indiana Jones (roller coaster), Alice's maze, Crush's coaster, Toy Story Playland, Cinemagique, Animagique.
- Shows/rides/etc that are different at DLP: POTC (slightly different, and no Jack Sparrow as of last December), Phantom Manor (similar to Haunted Mansion but different), Space Mountain (more intense!), Big Thunder Mountain (goes under the river and has its own island), Star Tours (it's still the old version and in French - personally I like the new version in English better!).
As for where to stay - I generally find the on-site hotels expensive, but did get a good deal on Hotel Cheyenne with Expedia UK, and got another good deal on the Sequoia Lodge using the two nights free offer that was running a while ago. The advantage of on-site is you get EMH and they're closer to the parks! A number of off-site hotels are easily accessible - a few of the hotels (including the Kyriad) run a shuttle service, while there are a few other hotels just one train station away (via the RER trains).