Nottingham tonearms compared to other brands?

I have experience only with the short (9") Space Arm, but I think that it's a great unipivot tonearm. It's much easier to set up than the VPI or Hadcock, by comparison, and it tracks very well. The armtube is carbon fibre thus the arm is quite light weight, so careful cartridge matching is a must, but with the right match it sounds great. The only caution is in regard to the tonearm wiring - it's very fine silver wire which requires a VERY delicate touch when mounting/unmounting a cartridge. Highly recommended.

Br3098, can you recommend a cartridge for the "Anna Arm" and the Space arm?

I have not but some here have; you could search the archive. If I remember right, the general consensus was that one would have to put an $2k or more Origin Live arm to better Spacearm mounted on the Spacedeck. I have no intention of doing it with my own Spacedeck. That arm is fine, just don't use low compliance and heavy MC cartridges.

Most high compliance cartridges seem to be the heavy ones. Would you consider the Dynavector DV-20X-H high output mc cartridge a good match? It weighs in at 9.1 grams but has a compliance of 12 x 10-6 cm/dyn .

I use Dyna 10X5 for now, but it is lighter. I know that many have 20X on their Spacearms and like it a lot. 9.1g is not really heavy. Spacearm's effective mass is about 9g so yes it should work just fine; and the compliance is okay. But again I have no personal experience with this combination.
I am thinking about trying some MM cartridge or perhaps the least expensive Lyra MC. But that Lyra is about $800 from the UK and more if you buy here.