Hello Scott,
If you are switching vendors, which ones have device level anti virus scanning on IOS? The answer I am afraid is none. This is not Symantecs fault, this is the decision from Apple.
As you are probably aware Apples apps are sandboxed from one another, hence a device level AV wishing to scan apps and data on the device will not be able to. So to fix this apple would have to open up their IOS source code to AV developers so they can develop a solution, Of course this means so can the malware / virus writers and apple do not want to do this.
You can learn about Kaspersksy attempt to ask Apple to do this so they can write an AV app here. It was of course denied.
http://www.zdnet.com/blog/btl/kaspersky-denied-ios-app-apple-buries-its-head-in-the-security-sand/77648
Apple secure their devices from malware through limiting the types of files that can be opened on iOS devices, securing their app store (yes you pointed out that app got through the check, but that is only one compared to >1million android apps with malware) and finally sandboxing apps. If a vulnerability is identified like the PDF issue last year, then Apple fix this with a security update to IOS
Of the links you posted, none have device level AV scanning, the only one that seems slightly different is the virus barrier app, this will do a scan, but ONLY attachments within the IOS mail app.
So at the moment there is no demand for an IOS AV, but more importantly, its not event technically possible. So switching your AV from Norton 360 would not be necessary
Thanks
Rich