Here's a rebuttal to a more recent but similar malware analysis:
http://www.forbes.com/sites/gordonkelly/2014/03/24/report-97-of-mobile-malware-is-on-android-this-is-the-easy-way-you-stay-safe/tl;dr - Most of the malware figures are derived from studies that include external app marketplaces in their figures. The total percentage of malware on the Play Store is ridiculously small and they're removed as soon as they're discovered.
They're mostly from shit apps with a ton of permissions, descriptions in broken English, and zero reviews. It's really easy to avoid malware on Android. Also, Android apps are sandboxed, so you can't extract data from another app (like your private keys).
That simply isn't true. The IOS apps are pre-screened for malware before being allowed in the store.
There are a lot of examples of malware that people got from the android app stores.
I am much more comfortable with a bit coin sitting in a closed ecosystem.
Android apps are scanned for malware as well. People can and do obscure code enough to get it through both stores, but not long enough to do any real damage.
Apple also has a higher barrier to entry for app approval (including paying for a yearly developer license vs a one time fee).