EGNOS is what we call WAAS over here. Its full name is the "European Geostationary Navigation Overlay Service", and it is differential GPS which uses the same protocols as WAAS and is compatible with it.

My unit is a Garmin GPSMap 60. I expect any unit will lose signal in woods. I see GPS as nice to have but not something I'd trust my life to. It's also jolly expensive, at least if you want one that includes maps.