Actually I don't personally have either of those two models - but I'm pretty sure they are solid shavers
My Birth Year is 2nd Quarter of 1967 So far in the M2 dating scale I have a Slim, Black SS, a long handle ball end Tech, a ball end travel razor set, A blue Lady Gillette starburst, and a black handled English Knack. Not sure if that runs the gamut for Gillette or if there is anything else out there. Because they were made in the timeframe, I also count my Schick type L1 black injector, L2 Stick Shick, type M1 adjustable and K1 Lady Eversharp in the group.
At risk of being branded a heretic, I give the slightest of preference to the Super Adjustable (aka Black Beauty). I also edge the Slim just a tink ahead of the FatBoy. That said, I have had my hand poised over the "vote" button for months and am still not ready to cast my ballot**. **In fact, I haven't used a Gillette adjustable in a couple-few months. I've been thinking about using one in a focus in the near future.
Are you asking how the BB stacks up against the FB and Slim? If so the Slim is better and I have yet to use my Fatboy.
My kids tell me I"m so old that I used flint. Actually it was a piece of obsidian. Hard to keep a good edge though. But I keep chipping away at it.
I've got a couple of D1 TV Specials, and a red tip. I keep my eyes open for a D1 Fatboy, but they are hard to find.
I thought about getting one... then I realized they weren't being made anymore by the time I was born!