I didn't have a whole lot of ink options, these were the only two at my Michael's.
The pens are SUPER scratchy on watercolor paper, so I got Strathmore smooth Bristol and put both inks in the same size pen (.3) and tested them out. It's always frustrating for me when things don't turn out like I expect - I really thought the Speedball ink would be better. I mean, look at its pretty bottle. And it's "super black" and anything with the word super in it should be amazing. Alas, much like my beloved Fabriano paper did NOT win the Paper Research Project, the Speedball ink SUCKS on every paper. Higgins black magic is what I'm going to be using for the next month.
Here are the pens, with the good ink, on the good paper. I actually have two smaller pens, but I couldn't get them to work. Yet. I'm a very tenacious individual, so we'll see about that.