I own a CT200U-EX but I've never ridden a 212 megamoto so I can't really say anything out of personal experience about it but here are my thoughts on both of them. I do feel as though they're much better than a CT200U in every aspect, and although I've owned a CT200U longer than my EX, the CT200U has had more problems so far than my EX. When I looked up the 212 Mega moto on their website I didn't see a fake gas tank on it while the EX has one that can't really carry much more than the little pack of wrenches it comes with, some bungie cords maybe, and a water bottle and a few extra smaller things. My friend used to have a baja mini bike that had the fake gas tank with storage and I liked it better than the EX's cause it had a little lock with hinges on it to open and close it, while the EX's just opens freely and is attached with a little string to keep it from getting lost. The 212 Megamoto also has a torque converter while the EX's doesn't, and it has a 5/8 shaft which you have to buy the adapter or kit from go power sports to put one on it. The mega moto also has a front and rear hydralic disc brakes while the EX only has a rear drum brake. Although the megamoto is $880 the EX is only $600 on each companies website, it sounds like the megamoto is more or less already all there with all you would need, while the EX would need some work to get it to where you would want it to be ideally. If you ask me, the Trailmaster MB200 is the one that has everything there that you would ask for and it runs for $900 on go power sports, only problem I'd have with it is why it doesn't have a storage gas tank like the CT200U and the bajas instead of a fake gas tank that does literally nothing but is there for looks. Obviously it is your choice but if I had the money and was looking for a mini bike that was completely ready to go out of the box I would ultimately get a MB200. Also the prices of these 3 mini bikes are different everywhere but I just pulled the prices I listed off of their brand websites except for the MB200. None the less you'll have a blast with either one you buy, but you should prob expect a bit more maintence with a CT200u-EX as their bolts and nuts tend to need tightend/inspected when you get it. Hope this helped.
Also, there's the new BT200X from Coleman to consider too-basically a CT200U+an EX combined
https://www.colemanpowersportsusa.com/products/bt200x