I think the Lions and Goff will surprise a lot of people and opponents.
Here is my breakdown:
Lions ><= RamsLions OL > Rams - Their OL has more studs with youth and they got a potential great in Sewell.
QB = - I consider Goff and Stafford a relative push (which 95%+ of everyone will disagree with).
Lions WR < Rams - WRs are a likely downgrade for the lions but there is potential. Brown of USC is a hungrier Robert Woods. Williams has more upside than anyone the Rams have but was injured all last year.
Lions TE > Rams - Hock is better than Higbee but not by a ton.
Lions RB = Rams - Swift is a lot like Akers. A little faster, a little less powerful. Williams who they got from Green Bay is a lot better than what I've seen out of Henderson. Depth key here.
Lions OC ? Rams This is the primary question mark of the season. McVay always has prepared teams though his play calling is questionable. No idea what we will see out of Lynn who did some good things with the Chargers.
Basically from what I've seen/red about the talent levels and players, I don't think the there is that much of a difference in Talent on offense between the two. It will all come down to coaching, health, and execution.
As to the defense. Lions will likely be much better versus last season. Rams will likely be a bit worse. Edge Rams but not 1st (Rams) and 31st (Det) like last season.