I bought a Wivamac 801 vario a couple of years ago. I did consider the Big Jet lathes and the Vicmark lathes when purchasing. My primary concern was to get the maximum over bed turning width. I felt the Wivamac gave this, for its price. The Vicmark machines were just too expensive. Where as the Jets were massive lumps of cast iron! Very heavy and big for the capacity they offered - this was a consideration for me as I don't have a big workshop.
Overall I am very happy with my choice. The Wivamac is a quality bit of kit. However, at the kind of prices these lathes cost I'm sure the others are good quality too. It's a question of personal taste.
Good luck in deciding.
M