Not sure where you're getting these stats from, Whoscored has him as only having played one game on the right all year for Arsenal, whereas at Barca he wasn't exactly setting the world on fire, hence why they sold him. It's clearly not his best position, that really shouldn't even be up for debate. He's best upfront, where we have better options. His next best position is on the left, where we have better options, then he's probably better as a number 10, where we have better options.
Just seems a daft signing, given his age, cost and the fact that we'd be shoehorning him into a team that really doesn't need him. I don't think well run teams buy player just because they are great, then try and figure out what to do with them, that's what badly run teams do.