Currently doing both so I can help. Firstly delete the myth about wam killers it's complete bs. If you study then it won't be.
Mgmt is piss easy but you need to think from a markers perspective plus they also mark really harshly for the first essay so it provides a wake up call to everyone but I heard it gets easier.
For econ 1203 it's my favourtie out of my 4 so I recommend it. In terms of maths it's stats which is different so don't conflate the two. In terms of difficulty if you have a good grasp of what stats is you'll be fine.
Since I'd don't know what your transferring into I can't say which to do but generally mgmt is comp for most business courses stats can be excluded for engo, Sci and actl etc