I'm comfortable on both, but can easily get bored on either one depending on the job. In building dies and tooling, some require extensive mill work and others require extensive lathe work. Two weeks on either one straight, then I'm ready for a break and go to the other machine for awhile. The ideal job t me though is designing a tool, setting up the 3 axis, then go run the lathe while the three axis is running. The best satisfaction is assembling the final tool, die, fixture, or whatever it is.