I wouldn't trust too much the announced weight and wouldn't use it as a criterion of choice between those different bikes!

They are all full steel, no titanium fork and rear triangle, a weight around 11kg seems already optimistic.

The Solorock has the L-twoo transmission which is better.

3sixtty is a well known Brompton clone brand that exists since a long time while other are unknown or appeared more recently. If frame quality is the most important for you, this is the best.

Take into account that an A-line Brompton list price is 1150USD without any discount. If you ever want to sell your bike, the price used of a real Brompton will be much higher than the one of any low cost clone (that with the currently huge shipment costs approaches the A-line price).