Not got any of the ones in the link but I have Bessey clamps and clamps based on the same design. The Bessey clamps are superb, a little awkward sometimes but superb. The other clamps I have that are on a par are Dewalt types;
https://www.screwfix.com/p/dewalt-dwht83831-1-parallel-bar-clamp-24/650hj
The thing to look for is the steel on the sliding bar itself and the construction of the jaws. The reason I grabbed some of the Dewalt ones is that the jaw heads are substantial, I'd say more substantial than the Bessey's personally. Lot's of clamps of this type kicking around, Rutlands have had their variants of Dakota and Rutland branded for a while, Axminster also have their own branded versions. I'd be inclined to steer clear fo the Ebay ones unless someone can (as you rightly ask) validate their quality and over a period of time at least.