Osb is useful as a subfloor and roofing material, although there are people who will claim it's useless for that too. It's almost completely useless in a woodshop though. There's no dimensional stability, no structural integrity. Wond hold screws, chips and flakes everywhere, it's just a mess
For jigs and sleds, embrace MDF. Now, you can't work with it in the exact same way as plywood, for example screws work different in MDF and you have to mix up how you glue to get the best results, but it's a very minor learning curve. MDF is also dimensionally stable, flat, and consistent. You won't find voids or imperfections in the center of a sheet like you can with plywood, and while you can get MDF to warp it takes some doing.
Now, for shelves and load bearing applications, stick to plywood, but for a workbench too, assembly jig, crosscut sled, things of that nature, MDF works fantastically