Both are extremely crowded; neither is really more crowded than other. They are among the three most crowded weeks of the year-- Christmas is the other one. As to your weekend assumption: Epcot, AK and MGM actually have their lightest days of the holiday season on Easter Sunday and day before (that has to do partly with many traveling in and out on those days and not going to the parks and partly with MK being a focus for most those days). That is relative though, since "light" at that time simply means the difference between crowded and extremely crowded.
MK is bad the entire time (think 2 hour plus lines all day all night for the popular attractions; even the Treehouse gets to over an hour) but Easter Sunday and day after are its worst. Everybody seems to go to MK on Sunday. Many of those believe something special happens there on that day that you cannot see other days of the week. That is a false assumption since nothing goes on at MK on Easter Sunday that you cannot see other days of the week. If you want a sit-down dinner in the evening in the parks, you must make a PS; walk-ups are often told there is nothing available at all for the entire night. Even counter service places get 30 minute or longer lines during meal times. PS's are needed at most resort restaurants too although you can often get them by calling a day or two before.
Best times to actually get on things without fastpass (which for popular rides run out for entire day before noon) are early morning and the following: (a) MK 4 to 8 p.m. for some things other than mountains, Pooh, Peter Pan, Dumbo which are always extremely crowded; also during a parade you may be able to even get on a mountain with only a 30 to 40 minute line (b) Epcot after 3 except for Test Track and Mars (Test Track actually gets to 3 hour lines); (C) MGM after 4 except for TOT and RnR and those have possibilities during the first Fanatasmic when they have two a night; (d) AK sometimes during last two hours park is opened it can be fairly easy to get on the popular attractions. Most crowded times in any park are 10 to 3.
Waterparks fill to capacity by 11 to 11:30, except on cool days, and then open up again after 2; however, the early birds take all the seats. Because it is usually warm and huge numbers go to the waterparks the risk of a theme park filling to capacity is less that time of year than Christmas but it might happen, particularly for MK. If there are two Fantasmics go to the second one because it never fills to capacity -- for first one you either do the dinner package or get there at least 70 minutes early if you want to get in. People start claiming curbside and other ideal spots for parades at MK two hours before; simplest is just to find an elevated area like the steps of Town Hall shortly before if you don't want to wait. Parks usually have longer hours (like MK to 11 or 12) during that time and early entry may be suspended simply because they will often open parks an hour earlier to everyone.
Also note that when Easter falls end of March like this year, Easter-time is usually worse than otherwise. Majority of schools still have their spring break either week before or week of Easter but a large minority simply have them every year last week of March or first week of April. Thus, you get the combined crowds when Easter falls during that time.