AT-101s (and AT-101Ws) can be great when new/clean, but I have owned 3-4 that were ravaged by age/dirt. I got a new one with a Dell system in about 1998 that served me flawlessly for years, but I have bought used ones that were dogs, even though they looked good.
Ripster is both right and wrong about Alps, they can be very sweet or quite painful. Once they get sick, euthanize them (save the keycaps, beige keys on a black board looks wicked).
Otherwise, Dells can be all over the map. They re-branded a lot of great boards.
The original QuietKeys from Malaysia are great, but later ones decline.
I have a couple of those modern small footprint types that are OK for rubber domes.
You can do worse than Dell.