Thanks David, that was very informative. I'm also trying to decide between exactly these two models, and having demoed both on at least 3 separate occasions now, my subjective opinions are quite close to yours. They are both very good actions - both feel incredibly solid and stable, and there's very little lateral wobble or bounce with individual keys (something that drives me crazy about my current Kawai). However, the Numa X feels slightly lighter and quicker without being lightweight, and the key texture is really superb - best in class for a digital. It's a small detail, but makes a big difference in my opinion. Overall, I think it feels very close to a well regulated acoustic. So based purely on action, I would personally choose the Numa.
However, there are certain practical considerations specific to my use case which favor of the Roland, so I'm still struggling a bit on which one to get. The Roland has built in speakers, which I probably wouldn't use that often myself, but my 9-year old daughter probably would, as she doesn't want to go through the hassle of loading a VST, routing the audio to external monitors, etc.
The Numa X has a headphone jack that she could use instead, but bafflingly, they've chosen to put it on the back of the unit, so you need to either snake the headphone cord underneath the keyboard or around the side in order to attach it without interfering with the keybed. This is particularly inconvenient if you plan to place the unit against a wall, as I do.
Then there are the aesthetics which are very subjective, but also favor the Roland in my case. While the Numa looks nice on its own, it was clearly designed as a stage piano, and doesn't integrate as easily within a home environment. The bright, multicolored, spaceship-like display panel probably looks great during a stage gig, but a bit less so in a living room. Likewise, the finished wood side panels look very nice, but unfortunately they don't sell a matching furniture stand, so you need to either use a metal rack style stand (undesirable for me) or build your own.
The Roland, by contrast, won't win any design awards, but it's much less flashy and unobtrusive and has a matching furniture-style stand available, so would integrate much more easily in my particular environment. I also already have the matching Roland 3-pedal unit, so that would be a easy integration.
All that being said, however, I'm still leaning slightly towards the Numa, as the action is the single most important factor for me, and I might be willing to put up with some of the other inconveniences simply for that reason.