I was sooo on the fence about d-cup and t-bucket, but every time I check them out I just ask myself if i really want another PID/coil/head on my counter. The answer is still no for myself.
The main difference is devices like the Dcup vaporize oils without passing them through a hot convection heat exchanger. This provides smoother and more flavorful vapor as you aren't mixing in convection air.
I'd like to see some double blind quartz vs sic vs ruby etc taste tests.
I've compared them all extensively on a dual XLR controller. That was how I first made the above observation that my SiC Halo on Slim Series base was smoother than my VROD with SiC Halo.
Beyond that the VROD is still probably the best single vaporizer for flower and concentrate, but there are some valid benefits of a separate setup.