Nik
if you only want to practice, then the modartt pianoteq is the way to go, but if you're like me, and the sound is a "VERY" important aspect for you, then you must try some high end sampled libraries, i'd recommend the native instruments and the vienna symphonic library (because both of them offer demo licenses)
i can also give you some of my favorites :
vilabs modern d (highly playable and realistic sounding, and it is the closest to a real grand in terms of features)
ni noire (a perfect allrounder with a perfect tone and recording quality, i'd get it instead of everything on the market)
pianoteq 280vc (the best ptq model so far, i like the clear tone and powerful dyn range)
ni claire (the most versatile one - you can make it sound like every key instrument but as far as a basic piano sound goes… meh)
vilabs modern u (a very cute sounding upright, and my favorite u p on the market with all the good features of modern d)
ni definitive collection (this one (three) is the best price to value on the market imo…
grandeur (very clean and warm sound, it's the best {among these three btw} when you're working on a modern arrangement
gentleman (i know people who swear by this one when it comes to making music)
maverick (a dark yet alive piano sound, very different then others but still quite useable on cinematic scores)
…
and now if you want to spend a significant amount of money on a virtual piano there's only one company that you should look into. vsl (vienna symphonic library) and my recommendations are :
yamaha cfx (arguably the best piano on the market)
bosendorfer imperial (rivals the cfx with some minor differences but has a warmer tone)
fazioli f308 (a linear sounding piano but with a lot of depth and presence)
steinway concert d (the most spacious and 3d concert piano i'm aware of but it has a sharp tone to it)
bosendorfer 280vc (very tight and in your face with a big dyn range, but the tone is quite intense)
fazioli f212 (very rounded and different, it is the calmest of all synchrons but the dyn range is limited)
bosendorfer upright (quite warm and mix ready, it is my second favorite digital upright)
c.bechstein (german) upright (a more colorful version of the bosie upright but it has less warmth to it)
bluthner grand (early 1900 cinema haha - it's beautiful)
hope that helps 🙂