Are the UNICOMP versions heavy? Like, physically heavy, like an original Model-M?
This is an important factor.
They are very solid, perfect for self defense

It feels a lot heavier than any other keyboard I've seen recently, but it's been so long since I saw a real model M that I can't say.
USB and the Windows keys outweigh any of the other differences to me. The key caps and action were the main things I wanted.