We have both SM Diamond (me) and FB Platinum (my spouse). Whether economy or business SM is the better bet for anybody who lives in the US most of the time IMHO. The exception is if you fly internationally often, where FB qualifies as Platinum after 70,000 miles if you live outside France and similar lower qualification for other elites.

Both programs get similar upgrades with each other, or are in the process of doing so, because they are coordinating fare classes and eligibility levels.

If you don't expect to make the highest Elite levels you amy also want to know that FB Gold is ST ElitePlus outside the US but only Elite in the US.

SM is an easy programs to understand and use while FB understand should give a PHD to anybody who masters it. On FB there are often different information in French, Dutch, English and Portuguese so one needs to be multilingual to figure out all the best ways to use the program. FB is the sort of programs serious gamers love to use because it is so complex and there are secrets too. For example there is a program on now that lowers thresholds for elite qualification but was announced to some eligible people and not at all to others, even though they're eligible.

So, if you are a masochist and love complexity go with FB and you'll not be bored. if you want simple easy and clear, go with SM.

I personally enjoy FB, but I may have diagnosed myself.