As always on used machines it comes down to fitted head stack and remaining
I have a habit of purchasing Otari Machines when the need presents itself,
as the US office is close to my operation. The machines have good parts
support and are fairly easy to "hot rod".
As for the Otari MTR 10 machines I try not to pay more than $500.00 USD(not
including shipping) for a two track machine. I usually modify the machines
into format specific uses.
Parts show up fairly regularly on Ebay to expand the function or maintain
the machines (i.e. Time code heads, revolvers, Control cards, Audio I/O'S
The other machines mentioned in your post are solid machines, but may cost
slightly more money to refurbish and maintain.
Just my 2 cents.
Cups 'n Strings Studios