I don't have a tea shop, would love to have one in far future, but not sure how to deal with dish washing (I always think of the hardest part first
If you are in Boston, probably either way is ok. But I would suppose a larger city like NYC can support a tea-only shop better. In rural area, I guess it would be extremely hard to run a tea-only shop.
In my area, the ok tea I've had out of home so far is from a restaurant. I personlly would rather have tea in a coffee shop than in a restaurant. If I open a tea shop, I would love to include coffee too, because I really love coffee. I would ban cell phone in my shop first, but keep the coffee and noisy coffee machine