@Yuhao, I have played a Roland FP-10 with VST pianos for about 20 months now and am also looking for an upgrade, with similar goals and wishes as you have.
Over the last six weeks or so, I made six visits to three different piano stores, multiple hours per visit, to really get to understand all those actions out there. At first, I also thought the differences from my FP-10 were only marginal (and indeed, it is rather nice at its price point and I really enjoyed it so far). But after gathering this much trial experience, differences really start to stand out.
Major things I got out of all this exploring:
- No (really, none!! apart from the hybrids) digital action feels like a piano. They do so in marketing only.
- The point is though, that a select few actions have you play like you would on proper acoustic piano actions. Meaning that technique, movements, and energy you put in can be quite similar (recognizable) to playing on a 'real' action. And that results in an easy and comfortable switch between such a digital action and acoustic instruments, making those few digitals useful as learning instruments.
- For me, no more plastic/folded action. (P515 and FP90 have folded actions.)
So out of all my trials it boils down to:
- Kawai Grand Feel III (in CA79 and CA99) (however out of my budget);
- Casio/Bechstein Grand Hybrid (which isn't a hybrid in the sense that the Avant Grands and Novuses are; in GP310 and GP510) (however out of my budget);
- Kawai RM3 Grand II (in VPC1).
My clear preference is with the Grand Feel III, but alas. This and the Casio are really close to eachother, my preference leans slightly towards the Kawai.
The VPC1 does a great job at its price level. In particular given that you have a hybrid as your North Star, I'd think this is a great step up to train yourself better and further towards proper piano playing. If your focus is on upright actions (U3) rather than grand pianos, the VPC1 might even be a more fitting choice than Grand Feel III or Casio/Bechstein. The pedal unit of the VPC1 is a much discussed and unresolved flaw, and indeed it isn't great. However quite a few people pedal happily away on it.
Make sure to do multiple store visits on different days in different weeks, and your experience and appreciation of the differences in the actions will grow and crystallize into your best pick.
Cheers and happy further trying,