I'm one of the crazy ones, then, because I like both plants, though one does have to keep on top of them.
Manxlad, Roundup does not affect the soil. It can be applied to single plants by cutting them down and pouring Roundup into the stem or by using Roundup gel, but you do have to be careful. I use it on plants that come up through my tarmac drive, such as alstroemeria, which is also pretty invasive, and they are always close to the borders and other plants.