Armory is certainly the best when it comes to security. The only thing i don't is that there are too many functions which can get confusing. Good and bad but generally is still the best. Using one right now after completed downloading the whole blockchain
Armory is a great option for people who are security experts and understand how to harden a desktop system against malware. A sandboxed, signed-code-only platform like ios is more secure for non security professionals. It uses the trustedBSD managed access control model for app separation.
Armory offers an easy way to put your coins into cold storage, which is the safest way to store your coins. Unless you can offer that on your iOS app, you can't say you are more secure.