Generally, the single biggest factor in piano sound quality comes from the sound board. Longer sound boards sound better. Grand pianos have longer sound boards than baby grands, and baby grands have longer sound boards than uprights. Obviously, there are different levels of quality of sound boards, so a short/high-quality sound board can be better than a long/low-quality sound board, but given that you are talking Steinway, then quality isn't an issue here.

There are some uprights that try to approximate the sound board length of baby grands, but there are really only a couple that I'm aware of.

If space is not a constraint---then I would always go with a grand/baby grand. If you are looking at a Steinway baby grand as an option, I wouldn't even consider plopping down thousands of $'s to refurbish an old piano (unless it is also a steinway, which might be a consideration as those can be worth a ton of $'s).

I faced a space constraint when I bought a piano years ago, so I went with an upright that has a very long sound board. It sounds wonderful, and is as close to a baby grand as you can get in an upright. It is a Yamaha U5, which is somewhat hard to find in the US. It is generally sold in Japan for people that desire the sound, but have space constraints.