Gift voucher arbitrage

I received the following emails today: What should I do? Are these two offers exactly equivalent? The John Lewis voucher somehow sounds better, because they sell better stuff. I could get (a fortieth of) a Macbook! Then again, I buy stuff in M&S more often, so the voucher is more likely to be used - and I could get a very nice dinner there for £25. If they'd offered to buy me dinner in return for my time, I'd probably be even better disposed towards them. And yet, if a client offered me £25 cash for 30 minutes work, I'd turn it down. Is it possible that I feel more positive towards B2B Marketing and Vocus than I do to my clients? Hardly. The only possible rational explanation is that I am less worried about establishing a reputation for cheap work in the eyes of a market research company than in the eyes of my customers. If this were happening, it would be a strange form of intuitive price discrimination. But this isn't really what is going on. It's...