Hi Twan,
good question. If you like the sound of the Toots Mellowtone but want a plastic comb, the Discovery 48 sounds more like the Mellowtone than the CX-12 does. For me, the hole form on both of these models is comfortable to play (Discovery: square holes but with rounded corners, CX-12: round holes) in comparison to the old style square holes on the 270 Chromonica, for example. A significant difference is that the Discovery has smaller channel openings in the slide itself (up&down hole placement) in comparison to the CX-12 (diagonal hole placement). That’s one reason why the CX-12 is louder. I also find that despite the longer slide traverse, the CX-12 has a faster slide action and is more airtight. So personally I’d probably go for the CX-12.
Hope that helps,
Steve