In the past I said that increasing 10m WSPR ERP was probably not worth it. However, I have changed my mind. G4IKZ (not that far from me) runs 5W and a Moxon beam on 10m WSPR. His ERP in the best direction is probably 10-13dB higher than me, and maybe even more. On RX he will have the gain of the Moxon in his favour. Looking at reports on WSPRnet today, he has been copied by far more stations than me and he is copying some decent stuff on RX too.
No, I think in more marginal 10m conditions the extra would be worth having. For now, I'll stick with the beacon and 500mW, but I may switch to the FT817 so I can run a bit more power on TX and listen too on 10m WSPR. My antenna is a compromise.