MS ER vs Citi Markets SA - London

I have an offer for Citi Markets Summer Analyst in London. The Markets program is rotational and includes two rotations on two of Research, Sales or Trading. I expressed particular interest in ER/research during the application process and they said they would try to accommodate me with a rotation in that. The graduate role is also rotational across these divisions before being placed in one permanently.

I am late stages into an MS ER SA application and I am fairly confident in myself for that offer. 

My question is: which of these should I take in a hypothetical scenario that I get MS too? I'm asking now because if I do get the MS offer, I won't have much time to decide between it and Citi. My ultimate goal at the moment is buy-side research/AM/HF.

According to II, Citi is ranked higher but I know in IB Citi is considered "mid-tier" since their IB practice is relatively new. I'm also aware ER is very desk/analyst-dependent but would it be possible to generalise here?

Thanks.