420 has more power and torque out of the box. Would be good for a large go kart or mini buggy. If you're really serious about going fast, you can certainly modify the 212 to put out comparable power to a stock 420 all the while revving way higher (way more top speed) for a similar price point.
- Stock 420cc (13HP/18FT-LBS) w/ 40 series TAV = $750
- Stage 2 212cc (15HP/roughly 15FT-LBS) w/ Juggernaut 30 series TAV = $740
But since you mentioned it's for your grandkids I doubt you want to go crazy with top speed.
Of course, but modding a big block gets expensive real quick. For the price of a stock big block and applicable transmission, you could have a small block that outperforms it. Similar power/torque but way more RPM (and less weight). More RPM means more top speed OR the ability to gear even lower than usual for more torque while still retaining the same speed. The latter is a huge benefit off road.can the 420 be similarly modded, though?