I see the Dippers handing out a hammering against Benfica, honestly wouldn't be surprised by a minimum of a +4 aggregate scoreline over the two legs with Benfica defending for their lives to keep the score down.
City v Atleti will be tighter but I see City controlling possession for most of the two legs and winning by a goal or two on agg after having to handle some real sh*t housery; that said I do give Atleti a 25% chance of griding/sh*t housing a result with Pep out thinking himself.
Bayern and Villareal could either be an easy win for Bayern or a hard fought win for Villareal, that tie will depend on how Villareal handle the first leg. Hold out in the first, they have a chance in the second, lose (even just by 1) and I think Bayern will win with some comfort in the second leg.
Chelsea v Real is the one that could go either way. I think Chelsea are actually the better team and a bit of a bad match up for Real, however they're what I now term a cup side as they are dangerous but do not have enough consistency to win a league. This game will be won in CM, who ever does that wins imo. Additionally, I don't see this tie as done even if someone wins 2-0 or 3-1 in the first leg.