Hello Jim and welcome. My first model from castings was a V10 by Stuart but it was so long ago I cannot remember if a had a mill or a vertical slide!
Either way, these Stuart models are excellent for people who have little or no experience with castings and Stuart castings are normally of excellent quality, but if you find one that isn't, they will immediately replace it.
Hopefully someone with more experience of using a vertical slide will be along soon with some more informative answers.
All the best with your modelling and please keep us posted on your decisions, they are sure to be helpful to others.
Brian