We've been to both in the past year.
Disneyland:
What I liked: Less walking, tons of attractions, good mix of standby and fast pass. 3 days was plenty to do everything. We walked from our hotel (HoJo).
What I didn't like: Big crowds even in the middle of the week, but even so there were no parades or fireworks because it was midweek. We felt priced out of Disneyland hotel and Grand Californian--looked and looked for discounts and couldn't find any for "onsite" hotels. Walking back to our hotel at night had me feeling a bit nervous, as the panhandlers were rather aggressive.
Disney World:
What I liked: The Disney "bubble"--the vacation starts with Magical Express. The resorts theming and service make you feel you're someplace special. You can spend a whole week and still not do everything, there's still something for the next trip.
What I didn't like: AK, Epcot, and HS feel like they need more rides/headliner attractions. With the parks being so large and spread out, they could really stand to have more rides! Also it takes precious time to get from point A to point B, which really sucks up part of your day and makes you reconsider the value of that midday break.
Hope this helps.