It stays in tune. If it doesn't then it might be a problem with your setup.
Feel differs from player to player, you might prefer the feel of something over something else. In other words, it's preference. Vai and Satch have their preferences, and so does Herman Li
I don't know about the mechanics of the EZ vs Edge, but generally if extra mass doesn't help contribute to anything it's better to cut down on it, from what I've learned. Personally the EZ feels robust enough for me though. Not to mention compact
I speculate that if there's a player who starts by using the Edge Zero, and plays an Edge after 20 years of using the EZ, they're bound to complain about the Edge.
So far I don't see many owners who complain about the EZ though.
With the functional improvements on the EZ, I think that the engineers over at Ibanez is doing their job. If not missing the mark means that they have to cater to a group of people's preference of feel while leaving another group to complain, then I don't really know what to say.. they can't please everyone.
For the OP, test out both of them and choose what feels better to you. Both of them stay in tune well.