My personal thoughts. The only down side to a circular section (post) style mill is every time you raise or lower the head, the potential exists to lose your XY orientation. Unfortunately that happens often with tool changes, even something as simple as a short center drill to longer drill to a tap. Yes there are workarounds but its yet another thing. IMO if faced with funds or space or both constraints, I'd probably opt for a smaller dovetail mill. Next step up would be an RF-45 style machine, which really doesn't occupy appreciably more footprint, just weighs more. Some people dont even bother with the stand which can vary from OK to cheesy sheet metal & mount the casting base it to a bench or home brew stand.
The other factor is accessories. A small machine dictates small-ish accessories because both the headroom, table & T-slots are smaller: vise, rotary table, related clamping systems, MT vs R8 spindle tooling, chucks.... Those cost money too, often as much or more than the machine. Yes they can probably be re-deployed or utilized a larger mill, But another train of thought is buy it once. Ihave seen guys do amazing things on smaller mills as long as the job suits the machine. So it all boils down to what you aspire to do. I think the RF-45 style is a sweet spot all things equal. About the same available head room as a baby BP, all accessories very compatible to an upgrade if it happens. The only thing they are lacking (if you want to use that word) is power & overall rigidity. But you could do many years of work before upgrading to something larger.
The other factor is accessories. A small machine dictates small-ish accessories because both the headroom, table & T-slots are smaller: vise, rotary table, related clamping systems, MT vs R8 spindle tooling, chucks.... Those cost money too, often as much or more than the machine. Yes they can probably be re-deployed or utilized a larger mill, But another train of thought is buy it once. Ihave seen guys do amazing things on smaller mills as long as the job suits the machine. So it all boils down to what you aspire to do. I think the RF-45 style is a sweet spot all things equal. About the same available head room as a baby BP, all accessories very compatible to an upgrade if it happens. The only thing they are lacking (if you want to use that word) is power & overall rigidity. But you could do many years of work before upgrading to something larger.
Space, 13 steep stair steps and a wife say it ain't gonna happen