I prefer a 135mm lens for most of my tabletop work. I own an Ektar 203mm and find that it requires too much bellows extension and has too shallow a depth-of-field for the magnifications I normally work with. I use my 180mm on occasion, but usually end up with the 135mm.
You'll have to try your 180mm and see how you like it. If you find, like I did, that it is difficult to work with, then go shorter. Your 90mm may end up getting you closer to the subject than you want to be, however. Maybe a 135mm or a 150mm lens is in your future?
Keep in mind, that a "general purpose" lens is not at its best at high magnifications. That said, I am more than happy with 8x10 prints of tabletop subjects at less than 1:1 from "general purpose" lenses.
If you end up doing a lot of close-up work at high magnifications, you may want to look at a "macro" lens. But for the occasional not-too-close-up, you really don't need one.
Best,
Doremus