I don't think anyone can accurately state that all grand pianos have heavier action than upright pianos. Grand piano actions can be all over the place as well, though generally speaking they will play more accurately than a worn out junkyard upright would be expected to play.
Here comes my entirely biased statement based completely on personal experience !
Something I can state accurately, is that my own grand piano of some odd 30 years of ownership had light action and I weighted it to be somewhat heavier. In trying out lots of digital pianos over the last year, the piano that came closest to the feel of my own grand was the Roland RD-700-NX in a blind store test ( blind being not knowing what to expect and I just had to keep going back to that 700 NX). Sound is a different matter, absolutely no digital piano has the resonance of a 6' grand piano period, not when comparing out of the box digitals to playing a grand piano live. Not at all, as it all has to be fed through speakers with digital. Now that's not saying they don't make terrific sound these days, because they do and it's not saying that recording of acoustic vs digital can't shed better light on the digital, because it can. But if you sit and play an acoustic and especially a good sized grand and then sit and play the digital sitting next to it, there will be a difference. The resonance and spontaneity of the acoustic is in live time and live feeling, it hits the walls and vibrates so, the difference is like kissing a real live woman vs a manikin I suppose ( never kissed a manikin but I can imagine). I can crank my Kawai up till it's ear spitting but it's just plain a bit different and that's that.
That said, I own both. A Kawai MP6 digital and the 6' grand and I love them both, as I never thought I could love digital equally ( for obviously different reasons). I must say though, with all this in mind, I absolutely would own just the digital if I lived in an apartment life style with close neighbors and wasn't planning to move to my own home any time soon. There just is nothing like putting on those head phones for absolute silent playing and good head phones make it sound like the whole room is sounding up ! I use Audio-Technica ATH M45 head phones, very nice, very pleased with the Kawai and these head phones. The Kawai action is very good, it's very slightly heavier than my grand set as I have each set ( four options on the Kawai, not so much for key weight but sound velocity from the keys with unlimited curve settings at that).. It took me two weeks to get the Warm Grand Piano sound and the touch curve to closely match my grand, FWIW. This includes damper release, damper sustain, note decay settings and note release, damper release sounds, as well as EQ and tonal settings. You can tweak till the cows come home with that piano ! I play it either or sometimes with both, the M-Audio studio monitors or the headphones. Today as I sit here typing I believe that I would sooner spend the money you are looking at spending on a Kawai MP10 than on either Roland you mentioned. The MP 10 is a notch above mine and sports wooden key cores. Both the 6 and the 10 already have action built similar to a grand piano action, including the sense of let off, a touch more so than the Roland I might add...
However, all that said, that's me !!!!! You really need to go out and try the pianos out for yourself. Not that it really does a lot of a good in this class digital, because as I stated I spent two weeks on and off with mine and you can't last that long in the stores. But you can quickly get the keys set up close and get a feel for that much. Don't depend on the sound in the store, any pro level keyboard is going to have so much control options for sound you won't come close to getting a true sample in a half hour store visit. You can however, get a sense of construction , weight of the instrument and the feel of the keys. Roland and Kawai are on top of it with upper end Yamaha's next for key feel. Any of the pro grade digitals will feel decent and be built better than the low end boards.
If you are looking to spend money on a piano I understand why you might buy a brand new acoustic vs taking a chance on an old upright. Just the reliability factor alone can be worth while. If you buy used have a tech really check it out. But there are some used grands out and about for a couple of thousand bucks these days too. Obviously not Steinway and generally not the top Kawais even but I've seen some decent older Baldwins around here.. Just saying. Again, in an apartment ? Get a really good digital with nice action from the mid range to top end Kawai or Roland is my thought. The dynamics of the Kawai incdentally? You guessed it, adjustable too.