I think for a system that had such small market share, NEC did a decent job transitioning to the all in one Duo. I think the Duo helped homogenize HuCARDS and CDs into just Turbo games. Using your example of Sega, they stuck with the Frankenstein mash of parts that was the Genesis/CD/32X that each required its own power adapter and had patch cords going everywhere for too long. While NEC had their period of doing somewhat the same, I think they moved on to an all in one unit sooner. When looking at both systems today, the Duo is much more readily available than the Sega CDX or X'Eye units.
I get the finance side of being able to jump in and get a CD unit just because you want it. But, when you can, I would suggest it. As stated, great games available. Like you, I love the PCE briefcase. That was the direction I wanted to go. But, I was able to obtain a broken dock and broken CD unit for pretty much nothing. Fixed both and so, here I am. As Gypsy stated, emulation is a route to experience CD games...I don't think emulation is the sin that some categorize it into. Emulation made me decide that I wanted the original hardware.
But hell, what do I know...I haven't even had a cup of coffee yet this morning, so I am pretty much babbling on.