Are the steinway D and B both good options? Or too similar?

It's very hard to figure it out. I've recorded the same midi clip with all of the acoustic pianos, with the same mic settings, and I just can't pick what I prefer. They all sound good to me. I just want something that sounds distinct compared to the steinway D's and the U4.

I think I would start by making peace with idea that you can, and probably will, buy additional instrument packs later. Your decision isn’t something you can never move past.

Personally, I’ve come to prefer the Steinway B (Prelude preset) for most of my daily playing. I listen through headphones, and it just sounds the most natural to me (coming from long ago playing an acoustic piano mostly in my living room, not on a stage). It has a such a sweet tone in the 4th to 6th octaves, and nothing is exaggerated; it’s not so wide it sounds peculiar, and no range seems over- or under-balanced.

Also, from a purely value standpoint, since you're getting the D, you get the Hamburg and NY variations (which are quite different).  The Petrof pack comes with both the Mistral and the Ant. Petrof, so by going with those you then have four concert grands to choose from instead of three.  The B is a great choice for regular playing, and most of my colleagues depend on it as the quintessential standard for teaching and daily use, but since I specialize in works with orchestra, I need the largest instruments and the greatest range of instruments possible.  Since you're planning on standard, you could get a larger pack/selection and scale the instrument down to the length of a B.

I usually buy a new instrument pack when it comes out or expand my collection with older instruments every other year (basically I buy grands without hesitation while expanding into more novel instruments or uprights tends to happen infrequently and during holiday sales).  So, the investment is fairly nominal compared to the upfront purchase of the software, which helps future decisions of getting additional sounds feel more reasonable, especially if you need to budget.