I’ve been doing a lot of drawing with ink lately, both landscape and architecture, and I’ve used a brush pen and regular red sable interchangeably.
This is wrong.
The sable is much better at making organic marks - like the bark of a tree, the texture if stone, grasses, etc. you have far more control over how much ink is on the brush and subsequently how much control you can exert.
The brush pen is great for detail though because it’s point is always sharp and inked. It’s great for drawing windows, rooflines and faces. The Kuratake I’m using flows a little too fast sometimes though so I’ll remove the ink cartridge and work for a bit with a dryer brush. I’ve also noticed that brush pen ink, in general, is more prone to bleeding. I’m guessing that it’s a viscosity thing.