Stay w/ 2 handed BH. There's a reason you went in that direction while learning. Unless you're a junior w/ 6-8 months to blow on learning a new stroke, new return, new defense, I don't see you getting significantly better. The 1hBH is technically a trickier shot to time and this also leads to dysfunction in form.
If you're not happy w/your 2hBH, take a lesson and see why you've plateued. Almost certainly you can improve it much better and quicker than by switching.