For me, it's TE.
First, because while Jarwin's receiving has been everything anyone could have hoped to see develop back-when (iirc) he was given the largest signing bonus in his class of undrafted free agents. But that, on its own, doesn't qualify a player to be a starting TE. It's admittedly a very anecdotal measure, but the fact that I've never watched a Cowboys game these last two years that he's been getting playing time, and heard him praised for a single block, but otoh, have heard him called out for missing a block... that makes me nervous.
Of course, there's a legit argument that if Jay Novacek could get it done, Jarwin is an inch taller and a few pounds heavier, it's legit to think Jarwin can, too.
Second, I can't say I know much about Bell, but what I've read leads me to think, as well as the fact that both Jacksonville and KC considered him not worth bringing back, he's not a #2 who could threaten to push for #1, but rather a #2 who could threaten to push for #3. Schultz, of course, has moved no needle yet, and his roster spot could be under serious assault once training camp cuts are made.
In sum, my perception is that Jarwin has been occupying his rightful role this last year or two, and still should be doing the same for 2020. He's that extra receiving situational TE you bring in, not the one you want as your primary, every-down TE. Bell is okay, as long as you have someone else on the depth chart who is, at least, his equal. We don't. So, I'm one of those who will be especially interested to see how our undrafted free agents out of Michigan and Portland State perform in preseason, and will be watching in the meantime to see if some new opportunity springs up from cuts off the Bears or Bucs rosters.
Trick question, right? ...fifty yard line seat on the 1st level.
