I'd take the 100k BA Miles because that can give you two F return tickets when used with 241 and GUF2. Even without those vouchers, that's worth a lot more than £1k in BA tickets.

I've just dipped below 1 million BA Miles. I don't feel special any more...

Luckily I should be back up to the 1 million mark by the end of my membership year though as I've got a couple of F journeys coming up, plus (cough) some Tesco points to transfer...