Hi - have been at both Easter and August. August is a lot quieter in the last couple of weeks but it is still fairly busy and you still need to be pretty well planned and organised. August is also cracking-the-flags, oh-my-god-I-can't-walk-to-the-bus-stops hot!! Easter is very pleasant in terms of temp and you can still make plenty of use of the pool and water parks.
The crowds at Easter are busy on the run up to the Easter weekend, over the weekend and a day or so after but both ends of the two week break are much quieter. We didn't feel bothered by the crowds at all. You have to be organised and ready to make the most of the first few hours of each day and well planned enough to make use of fastpasses and knowing which order is good to do the attractions in etc. But it's perfectly doable especially if you have our touring style of get there for opening, tour until around 2pm, leave and go back in the evening for a meal and shows.
The costs may well be higher though due to the flight prices (not that they are cheap in August!) but as it is getting closer you never know if there will be a one off bargain around - you would have to dedicate your life to finding it! Hotel wise, out of WDW, there will still be some reasonable prices around but depends what you want. If you want a villa there will still be some unbooked villas - you just have to find them.
Have fun!