As with most questions regarding machining, the answer is IT DEPENDS.
If you are looking at a decent volume of parts, then the additional setup and expense will pay off.
How are your programming skills? With a horizontal and the rotary table, you can do multiple sides along with the multiple parts. This is great for unattended machining.
Depending on how you approach your programming will directly affect the setup time. If working with a tombstone for example, if you approach each side and part with a seperate work offset you can easily become overwhelmed with many work offsets to keep track of. This can become quite confusing when making adjustments as one change may affect multiple other work offsets.
However, if you can program from center of rotation and have dedicated fixtures or vise jaws, setups will be a snap.
I love our horizontal. FWIW
Good luck with your decision!