Ang and Johnny Pow are currently doing it on the channel
Some Guy Rides. There are two main issues that I can see arising from using the Supercub over the CT125, and one main benefit, with a few smaller side-benefits. It's worth noting that JP has some serious skills, and Ang does not, so watching this is getting very Zen and the art of motorcycle maintenance vibes from it but for riding styles.
By far, the biggest issue that comes to mind is that the C125 and CT125 have different gearing. There's two episodes that cover the trouble that you'll hit with it. I crunched the numbers at one point, and due to elevation they were basically pushing overloaded bikes up bad terrain with about 5 hp. It was the sort of thing that if you had known that was going to be the case, a -2T sprocket change on the front for only this section would have been pretty appealing. The CT90 had the high-low range gearbox but even Ed March had trouble on that section, and he sort of glosses over it, but low oxygen + pushing the bike + bad conditions = bad time. There's plenty of sections of the TAT where Ang is gear 1/2'ing it, and that will probably be mostly gear 1 for the C125.
Short link including timestamp included below for your convenience.
Problem section #1
Problem section #2
Second main issue I can see? Carrying stuff. On the CT125 there's a lot more strap on points. It's fine and dandy for me to judge Ang from the comfort of my chair, but he's carrying WAY more stuff than I'd want to be carrying on such a trip.
Now, if you were selective with the TAT and knew what you were doing? You might be able to skip those portions and actually have a good time.
The main benefit is the same as the biggest issue: the gearing. There's large portions of the trail that Ang says he had trouble with where the taller gearing and the ability to go faster would be useful. Again, he's also limited by how much stuff he's carrying on the bike.
The series is astonishingly good and
I highly recommend watching it.
I have been hit with the same problem as you. Waiting, no news, even pinged the dealer to ask and got crickets. Talked to Motosport Hillsboro who as of Saturday or Sunday had the only CT125 shipment I've seen within 500 mi of Seattle (ever) - of course it was spoken for, but they offered me a C125 over the phone. 3 months ago I would have been all, "NO WAY" but honestly, I really took a moment and had to think really hard whether I wanted to wait. Ultimately I decided not to buy it, but... f**k me, I really had to think about it. FWIW, Brandon from Motosport Hillsboro and Lynette, the online coordinator - you're both fantastic people, and if I end up picking up mine in any way that remotely comes close to you, I'm dropping in to say hi to both of you.