I think absolutely the OP-1 is in the same ballpark as the Octatrack both in build quality and as an instrument - obviously mini jacks are not as robust as 1/4 inch, and it is smaller, but it is made from very high quality plastic and the case is solid aluminium. If you smash the keys like an idiot you will break them, same as a computer keyboard, but so far mine are holding up well, no build issues and I’ve had them for years.
I’d take an OP-1 or Octatrack over any Akai MPC/Force any day. Nothing against the Akai’s other than that DAW but not quite a DAW all in wonder box doesn’t appeal to me, if I were so inclined I’d just use a DAW instead because I don’t see what the advantage of the Akai’s are. I used to like the older MPCs though.