I also love Windy, and another similar app, WindAlert. I would choose either of those services in a heartbeat where internet service is available, though best practice is of course to compare different sources as well as weather buoy info where available.
I have used a Sirius weather subscription for about a year. I was glad I had it for cruising in areas where internet service is not available, but it did not at all live up to my expectations. I was looking forward to having the weather overlay on my chartplotter, but it was nowhere near as detailed as the two apps already mentioned. When crossing the Georgia Strait from Nanaimo to Pender Harbor, for example, Windy showed varying wind velocities and differences in direction all across the strait (strongest wind by far right next to Nanaimo). Sirius weather, on the other hand, showed wind vectors that were much less detailed and did not seem to take into account locational differences except on a much larger scale. I think Sirius weather would be good for offshore cruising but I did not find it especially helpful for inland waters. Wave height predictions are apparently only for offshore use.
I even had trouble using Sirius to download standard written Marine forecasts for the areas I was cruising in. They were usually quite sparse and abbreviated and were not necessarily close to my actual location. The worst was when I was cruising in the Broughtons for a month (where internet was unavailable and I needed it the most). Half the time, instead of giving me the report for the Queen Charlotte Strait, which is what I asked for, it instead would only give me the report for the Gulf of Alaska, hundreds of miles away. This was maddening and not the least helpful. (Wow, sorry, I did not realize this would turn into a rant.)
So what I am planning to use instead is the Garmin InReach Explorer+ device. The satellite subscription is cheaper, you can use it for two way text messaging, it can be used to send out an official distress signal, and the responders can communicate with you in real time as they are mounting rescue efforts. AND, it can be used to download weather predictions for any area, including wind speed and direction. It is not as good as Windy, but I have been experimenting with it and it seems to be much more helpful than what I was getting from Sirius. Oh, and it is small enough so that if you leave your boat and go hiking, you can take it with you as a safety device.