OP - clearly this thread has taken on a life of its own!
I think you need to cut through whether SHU or Aber has a better reputation generally or whether its prestigious generally, you need to look at the actual course.
Its not just MFL, its MFL and Business.
I can only comment that SHU (or Sheffield Poly) as it was back in the 90s was sought after for its Business Studies / International Business (with MFL) because as above, the option for a year in industry, plus a semester at a European uni wasn't offered anywhere else (other than Aston IIRC). Lots of unis offered a year out / 3rd yr as a teaching assistant abroad, or a placement, or a year at uni abroad, but SHU's course in offering the placement + uni abroad was fairly unique.
I appreciate that we're 30 years on now, and there will be lots of other unis offering MFL + Business, plus placement + european uni. I think however that simply for MFL + Business, SHU is still quite well regarded vis-a-vis other unis, given the experience / longstanding offering its had for this particular course.
The info about the differences between the 2 cities is also relevant - its a question of which you think would suit your DC. Good luck making a decision.