Why has this informational thread turning into an either/or argument with personal attacks? It seems to me that it is possible to install both with cost being the only real concern and I expect that as we get closer to 2020 affordable GPS WAAS sources will emerge. Take a look at the Trig TN70 and FreeFlight Systems 1201 boxes. Small, less than US$3000, and bound to come down in price as similar competitors emerge. (Note that the are pretty much identical boxes and may even be built by the same manufacturer - for example, Trig makes Mode S transponders for Bendix King.) In fact, given the prolific/agile/inventive soaring community, it would not surprise me if someone put out such a device as an IGC approved data logger with FLARM!