Another vote for Windy here. I like that you can look across different models, and you can pick a point in, say, the middle of the wallet and look at the different predictions there. You can also see a page comparing all the models for a given spot.
Does anyone find themselves choosing the model that suits what they want to hear, though?
As other people have said, most apps use the same core data, BUT some only take the feed once a day, others multiple times.
I use Windguru, but select GFS and both WRF models. The 25km model means that the weather is averaged across a square of 25km sides, which is not not necessarily as useful for local accuracy as 9km. But, the 9km obviously needs much more processing and is therefore more expensive for the publishers.
If looking for long-term trends I use expert charts from weatheronline.com(only available to subscribers) as you get the option to see the height of the 850hPa level, which shows where the jet stream is, and is available for up to about 2 weeks out on GFS and appears to be very accurate. As lows spin up and and travel along that level level it gives a good indication of whether your chosen time will be be "niceish or nastyish"