For those with a basement shop, floor space is often not the constraint for a full size mill; it is often headroom or access to get the machine into the basement. Of course, access may be a problem for a full size lathe also. BTW, the Atlas bench top mill is a knee type horizonal spindle machine, but a vertical spindle conversion can be fit up. My conversion is shop made with a separate motor and unusual spindle taper; but now commercial conversions are available that use the existing motor as well as standard spindle taper.
Mike