I haven't played 4th Ed, but I have played Neverwinter and what I can tell, the mechanics work just fine, with the At-Will, Encounter and Daily powers just being on different timers.

I haven't played DDO in a while and I can't remember much of its mechanics.

Neverwinter is a fun game while it lasts and is very pretty for a F2P (let's not get too bogged down here). It has a number of balance issues and a recent major patch has shaken things up a bit, so it's a bit unsettled at the moment. The economy last I heard was still screwed though.
You can hit maximum level cap and do all the content in Neverwinter without spending a penny, although some of the best end game gear is starting to be gated behind real money currency, which affects PvP significantly.

Neverwinter does feel and play much more like a standard MMO, so if Neovid says that DDO feels more like tabletop D&D, I'd take their word over it.


Ultimately I believe both are free to play, so there's no harm in trying each out for a couple of hours (unless you have download limits).