With Cybertron Prime, you need two. One to keep MISB, one to open. IMHO, as a toy Cybertron Prime comes second only to the 20th Anniversary prime.

Megatron, get one to keep MISB. Megatron isn't that cool. The vehicle mode spoilers are his feet. The ankle joints are weak, making it difficult to keep Megatron standing upright. If I would have know this, I wouldn't have bought one to open.

Starscream, you only really need 1 to keep MISB. That sucker is a brick. After having opened one, I'm 50/50 on advising someone to get a Starscream to open.