Well it depends how keen ou are.. Accuweather is very optimistic, so if I really want to get out, I check there..
If I cant really be bothered with going out, I check MWIS, as it is the most pessamistic of the forecasts
The met office has weather forecasts for individual hills, so it usually is the best for what it will be like at the summit instead of sea level..
I could waffle on, but my point is all the different weather sites have their place..