Since nobody has replied about the vertical table vs. vise, I'll comment. I've got a Palmgren milling slide with a slotted table instead of a vise, I've always regretted that. By the time you get a vise on the thing, you've got a whale of a lot of leverage on the compound. I replaced the lantern TP mounting forks on the milling attachment with a disk that fits the compound hole on the 9" S.B., it helped, but not a whole lot. Still a lot of leverage there, things moved while cutting. I made my own milling cutter holder for the headstock, cut off a large MT3-shanked drill, drilled and tapped the small end for a drawbar and bored a hole in the other for the cutter shank, secured with a setscrew. Still couldn't do keyways very well. Solved it by going with a Aamco shaper. I now have a small vertical mill for that stuff. The slotted vertical table was good in theory, being more flexible than a vise, I just couldn't get a solid setup that way.
Stan