[B.Reilly]

So, the title says it all. I have the option. The vertical is considerably more expensive, but controls are equivalent. Why choose one vs the other?

[mfgbydesign]

Ironic you write the vertical is more $; usually the other way around.
HMC advantages:
(Usually) already has a 4th axis
Shorter structural loop (Machine-Tool-Fixture-Work interface)
On an HMC you can machine 6 sides (or more) of a workpiece in 2 operations
Palletized machines enable change-over downtime on the order of 10 seconds
Large workpieces can be machined all the way around in one setup
Chips fall away from the work
More suited to unattended operation
Tombstones allow for multiple jobs to be set up at once or:
More operations for one job to be set up at one time decreasing lead time
Easier integration to other equipment using a palletized system (CMM, VTL, ?)
(Generally) better volumetric accuracy due to fewer axis stacked up
Size of parts have fewer limitations (doesn't have to fit under the spindle, can hang off the table, & the sky is the limit).

[B.Reilly]

So typically a horiz is more desireable... This horiz is massive, I'll have to see if it'll fit. The benefit I saw to the vert was it is easier for me to visualize the machining, it's more like the manual machines I've used. The HMC does have a pallet changer, coolant pump, oil chiller, and tool changer, but it's for hobby use, so most of that doesn't really matter to me. It does have the 4th axis, which I like.

[mfgbydesign]

VMC probably has a smaller footprint, lighter, requires less assembly upon arrival.
VMC's are good for flat plate work, as with a horizontal you would need a right angle knee, tombstone, or other attachments which can get expensive and you would need a jib crane or other means to load them onto the pallet.
Enclosures on an HMC can be very cumbersome & prone to leaking since the coolant is shooting out instead of down.
If there's no enclosure you will need to add some shielding to keep things contained.
I'm interested in learning more detail, & I'm in the same metro area; feel free to PM me for more in-depth discussion.