What is the best quality feel keyswitch for a thin keyboard?

[002]

Space Invaders are low profile?

Edit: So the wiki reveals they were patented as such. Maybe the patent compares them to less compact vintage switch designs.

Edit edit:
From the patent:

Keyboard specifications for electronic equipment for sale in many industrialized countries require the keyswitch housing to project not more than 17 mm from the attached printed circuit board. A keyswitch which meets the foregoing specification generally is designated as a "low profile keyswitch".

[Daniel Beardsmore]

It would be interesting to compare measurements of Cherry MX vs NMB Hi-Tek. I find that switches are often so much smaller than they appear in photos, and although there are definite indications that NMB were going for a compact design (with very little above the plate), the total height isn't clear (height of switch, and height from base of switch to top of keycap).

[Evilcamels]

You can see in the first image that the Space Invaders are similar height to MX when they do not have keycaps. Space invaders appear to be 1-2mm shorter than the Cherry switch.

Spoiler:

You can see the difference when the keycaps are in place, with the Space Invader gaining very little height while cherry keycaps extend the height a far bit. The key I used is DCS row 4, so DSA caps would shorten the switch a bit, but that would still be a 3-4mm taller than the Space Invaders. That would mean that a fully depressed Cherry MX switch with DSA caps would be the same height as a non-depressed Space Invader switch.

[Muirium]

Pretty compelling! Pity they're not still in production…