Android is better than iOS if you have multiple email accounts set up in Gmail.
I switched to an HTC One about two weeks ago from iPhone (I'd been using iOS for about five years). There are a lot of differences but one thing stands out as being worth switching for.
I have quite a few email addresses that I use on a daily basis: @gmail.com, @cameronhuff.com, @flatlaw.ca, @ontariomonitor.ca, @albertamonitor.ca, @summerhilldesign.com, @torontomonitor.ca and @federalmonitor.ca. These email addresses are used for separate business "identities" that I like to keep separate (it's confusing to get a reply sent to firstname.lastname@example.org from email@example.com). On iOS this wasn't possible through the Mail application.
On Android, Gmail is integrated nicely and when you reply it'll go out using the proper identity. This makes it much easier to run my different businesses on the go.
I'm not sure if this can be easily done on Blackberry.
If you're currently on iOS and have multiple email accounts in Gmail then it might be worth switching to Android.