Basis 2500, 2800 or Debut - which would you use?

They are all good. The Debut has the best overall Performance based on
its low frequency ability (it has to do with weight and isolation).
The Vacuum Option is very good, probably the best in the world (low
pressure, reliable, no - negative -influence to sound quality, top bearing,
good motor...)
Some time ago he had a technical paper what is done for what reason,
very clever solutions (the suspension for example).
In a way it is a tool for a record collector who isn't interested in any sonic
artifacts, instead it will show you very clearly what is on your records.
A lot of Audiophiles look for something they don't know, but they want
to have it. This is the reason why some many Designs are available and
all have their Fangroups.
I think, the Basis Design is for those who want a serious reproducer for
their music because they understand what is going on with it. Today, a
minority :-)
But I would buy it with a Phantom Arm instead of the Vector.

In the 90's I was a visitor from a Dealer demo, he had 5 Turntables on a rack, some very expensive ones (Linn LP12 max, Clear audio, Simon Yorke, Transrotor and a cheap Basis 2001 with Suspension feet, Rega 250 with Incognito wire and a Miyabi Cartridge)..all Importers used their Arm/cartridge of choice used the same Frontend and Amplification + Speaker, all carts got 47kohm, no damping ...
This little Basis was so superior to ALL that a few Listeners asked for another demo because they couldn't believe what was going on ... others were 8x the price...