I would definitely get the newer 5020 if you aren't paying too much of a premium to get the latest projector. There are some improved feature benefits with the new unit - but it's more evolutionary than revolutionary in my opinion. The fact that the new 5020 INCLUDES 2 PAIRS of 3D glasses (the 5010 doesn't) might make this an easy decision . . . BUT . . . if the price of the 5010 (after factoring the the cost of a couple of pairs of glasses) is somewhat cheaper, I would go with the 5010. It has been a projector that both consumers and reviewers love . . . and there is certainly nothing wrong with the image (especially for the price) to complain about.
Bottom line . . . I'd get the 5020 if it proves to better deal than the 5010. Maybe there are deals out there now with the 5010 being replaced? If so, I'd definitely scoop-up a great deal on the 5010.
If you do go with the 5010, it's nice to know that Epson hasn't, this year, reinvented-the-wheel with the newer 5020 projector. They are using the same chassis and are basing all of their new 3D projectors on the series XX10 designs. Even the replacement bulbs for the the 2012 projectors use the same replacement models as the 2011 product.
Just my two cents . . .