In M&M, the Mnemonic Enhancer provides a bonus to learning skills due to the enhanced memory of the user. Why doesn't the edge, Photographic Memory, give the same or a similar bonus? One would think the two are enough alike that the edge would afford a bonus as well.

well the mneumonic enhancer seems to basically improve your retention. You learn things easier. Where photographic memory remmebers perfectly. So you could recite the periodic table if you've seen it, and maybe a book or two on it, but that doesn't mean you ever bothered to learn it.

If I recall, there is a power in SOTA 64 for adepts that is basically an adeptmemory retention ( can't remember if it was eiditic sense, or some metamagic), but it also lowers the karma cost one.

Probably not the most satisfactory explanation, but it's a start!

You are misremembering.

The metamagic reduces karma costs(basically acts as Mnemonic Enhancer) while the adept power acts like Photographic Memory.

thank you, I couldn't recall which was which.

and the name of the metamagic, since the poster would probably appreciate it, and I don't have my SOTA64 handy?

Cognition Metamagic, and Eidetic Sense Memory (or 3-D Memory).