Skipping the discussion on patent, copycat yadda yadda, here is my opinion of the two different bikes after playing around with them for around 3 months. A Brompton Black Superlight vs 3Sixty electroplated.
Plant job: My Brompton Black has some paint finishing defects, minor but its there. My 3Sixty is chrome electroplated, so comparison is not possible.
Metal works: Brompton is brazed, not weld, and why they don’t sand down the excess bronze for the sculpted feel is beyond me, probably to retain the “welded” look. 3Sixty is a wildcard, the early version seems to have a couple of bad review on poor welding, but the copy I had has been pretty impressive.
My Brompton Black Superlight has also some poor finishing with sharp edges on the titanium parts, specifically the rear triangle.
Comparing my review sample of 1 unit each, 3Sixty is superior in this regards.
Hinge Coupler: Not sure what is the exact term for it but basically the coupling mechanism/joint on the stem and frame. 3Sixty design is superior, with the additional a round anchor at each of the 2 outer corners really seems to have some torsion support benefits, specially obvious if do not tighten the clamp sufficiently. Brompton is a old but tested and proven design, who am I to say a design that is older than me is no good? But if you ask me to pick one based on technicality, 3Sixty does have the edge.
3rd Party Support: Brompton ez win. All the well known third party parts are design specifically for Brompton frame dimension, most of the addon parts will work for both but do specifically note that 3Sixty has a front wheel dropout of 10mm. You will need to 3d print or source your own bushing if you want to use Brompton wheels(6mm qr) on the 3Sixty front fork. The chain pusher and tensioner compatibility is also a mix bag.
So what should you buy?
If you are the FOMO type of buyer, or like to do after market modification, Brompton is the way.
If you just want a good ride and not break the bank when your bike is stolen, 3Sixty is an extremely good alternative.
If you are a extreme modder, you can consider 3Sixty as well, or just build your own bike from 3rd party Titanium/Carbon parts maker.