A few comments in the hope that they are helpful:
In my experience with several samples of each, the Cav Arms handguards are far, far better made than OEM plastic handguards as delivered on various Bushmaster and CMMG products. They are a different material with a nicer texture, more thickness, and much more solid lock-up.
I have one M4gery with true double heat shield handguards. I hate them! It locks all the barrel heat inside, so your barrel stays hot much longer. Sure, it will help your hands in the brief time between when the barrel gets really super hot (400? 500?) and when that heat saturates the outer heat shield (?), but I hardly ever fire so quickly for the barrel to get that hot, and the unvented outer heat shield is death to the barrel by keeping it so hot.
To me the MOE carbine handguards are OK, but somewhat of a disappointment. The shape is good, the material is fine, but they don't attach as solidly as a couple different sets of Cav Arms handguards I've tried, and mounting rail sections to them is somewhat clumsy. They were a disaster with a rail and a VFG attached to the rail. They would probably be OK if you just wanted a little rail section for a mini-light or a side sling swivel.