Honestly, if I were given the choice of a new A4 or an old 90 like this, I'd take the 90. The body is classic. The interior is timeless.
In "Audi-speak" this is a B4 90. It was the last car to be badged as a 90 (and, in Europe, as an 80). In 1996 Audi replaced it with the A4.
Audis from the 1980s and 1990s are prone to electrical glitches, but they're usually not disabling. At some point you may have to deal with a window motor or a non-operating sunroof, minor stuff like that. In my mind, that's a small price to pay for a car that looks and drives as nice as an Audi 90 quattro.