Stats per 90 mins. Shaw left, Dalot right.
Baseline BPS is the key. Those are BPS they acquire per 90 mins excluding goals, assists, cards and clean sheets. A clean sheet is 12 BPS so if United win say 1-0 then Dalot will on average get 26 BPS while Shaw 23. So on average Dalot will likely be in bonus contention, Shaw likely won't.
Whether past BPS has any influence on future score is something for you to decide. For me Shaw is obviously the better footballer but the BPS is seemingly more tailored towards Dalot. Neither is going to give you attacking returns every other week so ideally you'd want to pick the one more likely to compliment the clean sheet with bonus points.
Always nice with stats. To play devil's advocate, Shaw (according to stats) was one of the players with most attacking passes during World Cup. Top 3 I think. So he's in good form apparently.