I would think the litter box would get really messy quick, wouldn't it? Litter sticks to my cats feet and he has med/short hair, and the litter winds up all over the place. Not sure if doggy litter is any different but I prefer the pads, quick and easy clean-up. Plus you can get a few of the washable kind so you never run out and they're super easy to clean, just toss in the washer
good luck, no one here frowns on you for doing a dual training method. I have and it's paid off big time!