Most of the apps work on iOS(Apple) and Android, so no real difference there. The two most common ones used in the US for our type of aviation I think are Foreflight and iFLY. Both charge an annual subscription with regular updates etc. If you own an iFLY GPS it's about $20 more to get the app (works the same) to put on a phone or tablet.
There are much cheaper GPS apps if you look around but either not aviation related or no updates etc, but they do work if you don't need all the bells and whistles like airport information etc
Easy to get costs, just go on their websites.