I can't really say a lot about the Neo Geo X and it looks like it's hard to find a new Caanoo these days. The Caanoo is able to run about 95% of the Neo Geo games(not via Mame, which is quite bad at emulating them) via GnGeo, but you'll have to do some research to get them work.
I confirm that Caanoo is really perfect to emulate almost 80% of the MVS portfolio, in virtue of the 4:3 low resolution screen. Anyway, you need the roms to be dumped exactly. I think I am not allowed to post the link, but make it in google "gngeo caanoo romset" and you will find it.
More, I think it is cheaper find a used caanoo on ebay than buying a new Neo Geo X. Still Neo Geo X is limited to few games for now.
Just use MAME and GnGeo on the Caanoo..Gn Geo works awesome, but a lot of the games don't work properly. Some of them that don't work in GnGeo work in MAME though if it's the right version and whatnot. You just have to do some research and your own trial and error.