I have 5 6" vises: a Kurt, an Autowell Kurt clone, a Eurovise, a pretty typical offshore clone and an old beat up early model Kurt. I've had a chance to compare them to Glacern and Orange.... The best quality for the price seems to be Autowell. It is probably sold under other brand names as well, but is a very high quality Taiwanese Kurt DX6 clone. It is about 1/3 cheaper than a Kurt and less than 1/2 when on sale.
I know some have had good experience with Glacern, but I have seen one stripped down, and wasn't impressed with the internals. When indicated, it seemed to be rigid, but not quite as good as Kurt or Autowell. This was 5-6 years ago, so I hope things have improved since then. Orange vise seems to be a pretty typical offshore vise rebranded. I was appalled by the poor quality internals and the indicator readings showed that this particular vise was pretty flimsy.
I bought the Kurt, Autowell and the Offshore clone all brand new. I paid CDN$ 700 fo the Kurt, 500 for the Autowell, and 200 for the offshore one. the other vises came with machines. I wouldn't recommend the generic offshore clones any more. 30 years ago they were quite good, but now - not so much.