Manamorphose was a common in Shadowmoor, and was reprinted in Modern Masters 2013 as an uncommon. It is extremely reprintable, and it's inevitable that this will happen. Therefore, this is a short-term to mid-term spec.
You can see the momentum on this right now... this is clear as day, and sees widespread Modern play. Further, it has a potential role in some Legacy decks.
Get Foils now around $6 - they will spike to $15 in a couple weeks. These are your best bet overall.
Non-Foils are around $3 right now, and will spike to $8 apiece, stabilizing around $5. These are less protected from reprinting and have less upside. Still a fair spec, though. Stick with Foils.