well, I'm spoiled in a way that I only practice on the school's Steinway...
but I grew up with a Yamaha upright...
When you say a grand piano is better, I would say only a good grand piano is better
for steinways, you need a very very old (50 years or more) before it becomes so great
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the biggest difference is the key...
upright piano uses hollow keys so they're very light
grand piano uses solid wooden keys
and you can see that for everykey there's a hole drilled to put in a piece of circular metal that makes it even heavier...
the greatest thing is that when it's heavy it's a lot easier to control...
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the bad thing about an upright is, as soon as you touch a key, a sound is made
grand piano, you need to pass a "threshold"
if you feel it you'll understand...
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but generally if you have a yamaha, you'll never go wrong
every yamaha feels the same... so it's "safe"
all steinways are made to be good, but not all are easy to play on
brand new steinways for examples, the pedals are usually so stiff that it's hard to do rapid pedal change (for instance in scale passages where you change the pedal almost as fast as a trill)
i play on 100 year-old steinways (2 of them),
experience is... whatever you dream of, it happens on it...