Flex help- Chark or J. Brown?

Can’t really decide who to drop in flex spot… DJ Chark is good. But Bills has a good matchup against Miami this week. And John Brown could ball out

Here’s my Week 7 lineup:
QB - D. Prescott
RB1 - D. Johnson (Got Chase waiting on bench already)
RB2 - P. Lindsay (I know… I know)
WR1 - Julio Jones
WR2 - T. Lockett
TE - E. Engram
Flex ______ Chark/Brown???
K - R. Gould
DEF - Bills

Both look like viable options this week. HELP! lol

Chark’s matchup isn’t the greatest, but he’s been a stud the majority of the season and I’d start him over Brown. Brown’s also dealing with a groin issue