I have Just ordered watercolour paints but also seen these alcohol artist’s markers? Is there much difference especially for urban sketching?
IMO your are asking for completely different tipes of media. When I draw outside, I just take a graphite pencil for the sketch and go over with technical ink pencils.
If I would use colored sketches outside, I wougo for markers or grab some colored pencils.
Anyhow, using watercolors, you might need a decent paper to deal with lots of water. For markers, you very smooth paper might be most effitient to avoid bleeding.