BnW
I'm currently on the hunt for a new keyboard and demoed both the FP90X and P-525 over the past week, so I'm happy to give my thoughts. FWIW, I would characterize myself as a high-level moderate to low-level advanced player - pretty comfortable around the keyboard, but by no means at a professional or virtuoso level.
First of all, if you are able to try them out for yourself before buying I would highly encourage it, because the actions do have quite a different feel and you may have a strong preference for one over the other based solely on that.
Between the two of them, the FP90X strikes me has having the more robust and substantial action, with the P-525 feeling a bit lighter, though still solid. My personal preference was pretty strongly in favor of the Roland, as it felt more realistic to me and would probably serve you better in the long terms as you get more advanced, and/or want to feel comfortable going back and forth with an acoustic. But if you're just at a beginner or moderate level, the P-525 is perfectly fine, and will probably feel easier to navigate.
In terms of sound, I don't think the internal keyboard sounds of the Roland are really its strong point, though they are perfectly serviceable. But if you're judging purely on piano sound, the Yamaha is probably better in this regard. Both seem to have decent enough built-in speakers if you plan on using them.
I know you mentioned that that you don't plan on using external VSTs, but if you ever decide you want to explore that route at some point in the future, the FP90X has a built-in audio interface, which makes it much easier to play external audio though the built-in speakers using a single USB connection. I believe the P-525 only has analog audio inputs, which might require a separate audio interface depending on your setup. Just something to consider.
Anyway, hope this is helpful. Like I said, do try to demo them both in person if at all possible.
