Parka Blogs has a great series on the tools artists use. Urban sketching is hot these days, and one of my favorites is Shari Blaukopf. Here is a link to a detailed breakdown of the tools she uses.
I notice that, like a lot of other sketchers, she has some favorite pens but hasn’t yet found some of the wonderful stuff that’s out there. One can’t specialize in all the tools available, but I really love both good pens and good brushes. To some extent, those involve personal preferences, but at a technical level, some pens and brushes really are better than others.