Don't know whether many will have both iThings and A-things... to compare apps side by side...
I do. And I'm a developer for both platforms.
In general:
- If only one platform is supported, it will be iOS (there are some rare exceptions for boating apps).
- If the same app is available on both platforms, the iOS one will be more advanced and have more capabilities; the Android version will eventually get those capabilities but sometimes not.
- The better apps are the iOS ones. This goes outside boating apps too.
If you're only going to get one type of tablet, it is better to get an iPad. Even outside boating, the apps are just better. The people who don't follow that are typically trying to spend less money (and getting less capabilities) or have some bizarre dislike for Apple's unbelievable success. Owners of iPads often give up their laptops and will fight before giving up the iPad once they've had it for a year. Android tablet owners never feel that way. Android ownership is significantly skewed to phone ownership too over tablet ownership.
For what it's worth, I like Android a lot and I write for both platforms whenever I write anything. When I give talks at rendezvous, etc, I often ask for an Android/iOS split. It's usually 60%:40%, iOS:Android today. It used to be more tilted to iOS but all my boating/developer friends except 1 still write for iOS first because they make more money there. iOS users tend to buy apps much more than Android users.
And it can't be said enough - if you get an iPad for use on a boat, always get a cellular one so you'll have a real GPS inside it.