Apple regularly loses security shootouts, and is widely derided by security people. Their only advantages are their niche status (which they are losing) and their lack of consideration towards old apps (they can dump old APIs which are hard to secure, and make other backwards-incompatible fixes, because they just don't care that much about backwards compatibility).

Apple isn't a niche player in mobile. Wether you like Apple's App Store or not, in terms of security it's a raging success.

The other big advantage on mobile is a closed ecosystem and mandatory sandboxing.

This is a rather biased view. Maybe check that top ten list again.

The one that Apple holds two positions in for arbitrary code execution vulnerabilities?