I just went through this same back-and-forth debate with myself a few weeks ago. After much research into Better Bottles, and literally adding the whole setup to the shopping cart on Northern Brewer, Austin Homebrew, Midwest, etc. like five times, I never did pull the trigger. After some discussion with Forrest from AHS, I decided to go with a new bucket/lid to replace an aging yellowed one. I got the biggest one they carry under 10 gallons (7.9 gallons, I think), and I'm glad I did. Plenty of headspace for primary fermentation, and if I really wish to rack to a secondary, I have two 5gal glass carboys sitting idle most of the time (if not filled with graff cider).
I just found that the initial cost of the Better Bottles with the fittings and racking adapter was too high for what it gave, and only having 6 gallons for a primary didn't appeal to me. I don't have time to watch for blowoff, not being home all the time, so the extra headspace in the bucket clinched it for me.
I'm thinking about drilling and bunging a larger hole in the lid to take samples through. May be an option for you, as well.