The deal with Snow Report apps is that they all get their data from the same source (it was two sources but I'm pretty sure Vail bought their one competitor and it will become one source soon). So even thought the UI might be different (of those apps I like OnTheSnow myself) the data is all the same.
Now that I set you up Powder Alarm is my favorite (though I built it too, so maybe I'm biased). www.hibabysoftware.com/powderalarm
I use the actual snow hourly telemetry data so can do cool things like wake you up at 5 am before OnTheSnow has updated data.
For non-snow report apps I think its hard to beat solipskier for a game.
Ullr's Mobile Avalanche Safety Tools www.ullrlabs.com/solutions.html