Albert,

Android apps, if you have your GPS or phone on all the time it will drain the battery much quicker. If you are turning on the phone just to scroll through maps not as much. Not sure about the program you got for your android but I know Backcounty Navigator will cache (store) the maps locally on the phone, which is critical when there is no wifi or cell coverage. A friend used his Garmin phone on our trip from Crescent City to SF in August and it worked out well. Local maps are key.

Microsoft Silverlight is just another web plug in that allows more client side functionality. Think of it like Adobe Flex/Flash, Reader, etc. I'm pretty sure people use the app all the time at work on iPad via a web browser all the time so it should work fine. I have been trying to get them to buy me an iPad for a while; maybe I will use this thread as a reason why I NEED one. There is an Esri ArcGIS iOS app in the iTunes marketplace if you want to try that as well. It should have access to the same topo map service as the web-based version.