Working as a hospital chaplain means I fill out a lot of paperwork, including carbon forms, so after spending my internship using a Cross BP I decided to treat myself to a Caran d'Ache 849. The Goliath refills are reliable and don't get gunk buildup like my Cross refills did. Smooth? Well... relative to ballpoints, I guess it writes okay. I love the hexagonal barrel. I chose the bright red color so I always know which pen is mine when I'm on the floor.
I like those little CDA pens, have a couple. For me, the refills last a long time but the blue refills were just too faint - smooth, but not dark enough. Those refills are unique for the pens, I've never found something that can swap in there.
I guess I'd give a partial nod too to the Waterman refill. I have several Waterman BPs that are pleasant, but I don't find the refills as smooth as Lamy or Parker.
Yes, it's definitely all in the refill when it comes to BPs.