It's so dark (the picture) that I can't tell if it's a croton or a dieffenbachia, though I'm pretty sure it's a croton. If you can get a better picture, post it on the house plant forum and lots of people there will tell you about it.

The leaves are specked with white, though. Both the plants you listed had streaked leaves.

Dieffenbachia, croton has a different shaped leaf..as I remember.

Croton comes in many types and on 2nd look I'm sure it is a croton, not dieffen.