Flex decision WR or RB?

Helllooooooo Ballers,
Going into the first week of my league of record to defend my #footclan title. Here are the facts
Standard League
12 man
currently have Terrence West in my flex - other RB are Demarco Murray and Dalvin Cook
Current WR are D Thomas , Dex Bryant

Should i swap my Flex for another RB or Switch it to a WR i feel that RB have higher upside? Here is my bench = Ameer Abdulah , Pierre Garcon , Adam Thielen , Tedd Ginn JR, Randall Cobb

Thanks footclan hope im not too late here