I spent way too much time over thinking exactly the same thing – whether to go for the big or the small pump – main reasoning was for aesthetics rather than practicality.
Wanted to ditch the pack, but have the basics covered for a couple of hours local ride, without having a massive pump strapped to the frame looking like you’d fallen into Halfords in 1993.
Opted for the smaller pump and i’m pleased i did. Straps to the frame and is pretty inconspicuous as its the same size as a normal bottle (get a black one to mask it even more). EDC tool in there, and there is actually a small storage compartment in the bottom that i managed to get some patches, bacon strips and a 2x small zip ties. Tube, CO2 and tyre plug tool strapped to the frame.
I’ve used the CO2 head and the pump in anger and they are really good, even though it is the smaller volume pump. Its well made ad the tool is pretty trick inside it.
I do plan to get the little EDC Tyre plug kit and mount the spike plug on the bottom of the tool as it will fit inside the small pump as well, but i really struggle to justify £32 for it.