I suppose I was a bit contradictory in there. I didn't mean to be. Let me enumerate.
2.5# and up cylinders almost always cost less over time in terms of filling. Quite simply, welding shops tend to charge less per unit of CO2 filled than do places like paintball shops.
My reasoning in the last paragraph in the post you quoted was as follows: In the 60-P stand that I built, my CO2 setup takes up a relatively large amount of space. I would rather use this space to put in some shelving units or something similar to aid in storage of my fertilizers and other tank parts. A paintball setup is smaller than my current setup, so that would allow me to have built in shelving units to the stand.
It is more of a storage thing than anything else. I live in a college dorm, so space is pretty limited as it is. I a lucky enough to have enough room for my setup, so I just wish I was able to use the space in my stand a bit more effectively.
Sorry if I caused any confusion in the post you referenced.I hope it is clear now.
On another note, I would like to meet up with some locals some time. I am fairly minimalist when it comes to plant selection, so I probably won't have much variety. I tend to favor foreground plants, since my current tank is an iwagumi. I am going to try to do some immersed growth near the end of the school year and during the summer, so hopefully I would have at least a decent amount to trade by then.