I prefer the DIY method. It isn't pressurised at all. It's cheap. And,..uhh, it's cheap. I have also heard that it often does a better job than expensive pressurised systems. Works fine for me anyhow.
Having done both with small and large tanks, I can say I feel the opposite. DIY is horribly inconsistant even with 10 bottles hooked together and rotated for refill, and The money I spent on Sugar and yeast would have quickly paid for all the co2 eqipment I now own. I will say I did not run out and buy a high dollar set-up from the LFS, but rather gathered and matched less expensive components. The only thing I bought at a high price was my manifold, and it was worth every penny since I'm running three tanks from one bottle. I currently have a 20 pound bottle running, but recently aquired a 40 lb to replace it with. with a 115g, a 15g, and a 10g. I use 20 pounds in about 9 months and maintain Co2 somewhere between 50 and 75 ppm in all three tanks. I simply could not do that even in the 10g with the DIY.