I've been using the XM weather on my AFS for over a year now and I love it. I've never used a 496 though so I can't give you an apples to apples comparison. I just subscribe to the lowest level. $32.31/month on my credit card
Speed - It takes about 5 min to get the first info usually and there is an update about every 4-5 min in flight. I think this is similar to any XM system as far as I know.
What you get
- radar overlay on moving map
- Metars when you pull up airport info
- flags indicating VFR/IFR conditions on the airport circles on the moving map
- TFR Overlays on the moving map
Great stuff, but I think XM charges too much. I like the idea of free ADS-B, but it wasn't really an option when I installed the XM. The NavWorx box seems like a great option on the East coast at least, but I don't have any first hand experience with this system yet.
Greg
RV-7A