From my point of view, I fly mostly BA, but it was never enough to even get Bronze never mind anything else.
With BA changing their scheme, I became aware of RJ, and thought would give it a shot. While I'd probably have hit Bronze on BA this year through segments, the risk is better if I can get to Gold Hawk on RJ for 2 more segments, and get more than BA would have ever given me. If they change the rules, then I've not really lost anything as I wouldn't have gained much with them anyway.

That said, I'm hoping to get Platinum by mid-December and secure the benefits for 2 years (and possibly 3 if they do a soft landing to Gold if I don't re-qualify).