Probably neither one. Well, maybe the throwout.......
Odds are your clutch is out of adjustment and not disengaging all the way. It could also be a problem with your pilot bearing or bushing.
If the input shaft is spinning with any amount of force, then its going to be hard to shift into any syncro gear, and would grind in a non-syncro one.
Also going to be hard to get out of a syncro gear.