Power on 10m WSPR

There seems to be an advantage on 10m WSPR with a little more power. VK2KRR was using 10W when I copied him earlier. VK5MR who copied me just once today at -24dB S/N when I was using 2W probably would not have copied me at 500mW. When conditions are good, more power does not make sense as 500mW is enough. When conditions are "just" there, it seems more power helps. So far today I have been spotted just once even at 2W TX. With 500mW I would probably not have been seen by anyone.

UPDATE 2052z:  After a promising start 10m WSPR was a disappointment today with just G spots since this morning.  It looked very promising early on.