I’m currently involved in discussions with many Content Service Providers(CSP). Even though the discussions are around connected TVs and tablets, CSP usually disclose their result in terms of downloads on purely mobile platforms.
The ratios between platforms are surprisingly stable from one CSP to the other.
The ratio they get is roughly 1 download on Windows Phone for 10 downloads on Android for 100 downloads for iOS.
One can expect the ratio to improve on Windows Phone with the upcoming launch of the first Nokia Windows Phone mobile due next week. Never the less these ratios help to make up one’s mind in term of platform priorities.