Google also has content control. You can't develop a virus and stick it in the Google Market, they will remove it. The only real threat, as with the iPhone and iPad, is downloading apps from sources other than the official stores. And whether using iOS or Android, if you do wind up getting a virus, you deserved it.
Not many viruses exist for either OS because there just isn't a reason for them. It is much easier to develop an app that legally takes your information than to develop a virus and ways of transmitting it. Why bring a virus to them, when you can develop an app that actually gets people to download it. Neither company is very strict on what information apps can collect.
Why worry about viruses, when both Apple AND Google allow app developers to collect information from you, from legally marketed apps, that don't even make sense for the app?
1) Google had no content control whatsoever for a couple of years. Literally anyone with an e-mail address and 10 bucks could upload anything they wanted.
2) Google still prunes out about 30% of applications monthly after release to market place due to malware behaviour, also since Android is open for external sources it's dead simple to create a "harmless" app that injects malware code in the phone from an external unrealiable source in form of software update
3) Android OS release model puts the task of updates to the operators. This has lead to operators making changes to Android - called operator back doors. They're a nice and convenient way to bypass any and all security measures built in Android and this is where the inherent insecurity of the Android model comes from. It has NOTHING to do with linux.
4) It's far easier to create an app that calls to payphones 10 000 dollars a pop instead of creating a killer app that everyone wants.
Statistically about 30% of apps in Android store used to have built in malware. And that's just in the official store! Now Google is playing catch up but still plenty of external uncontrolled places to get infections from
A smart phone is almost directly equal to your credit card. Would you let your credit card machine have back doors and/or load stuff to it from non-official sources? I bet not. I wouldn't. The only way I'll ever use an Android phone is by pre-paid cards. All the people who got 6 000+ euro or dollar bills from operators have lost the legal battles in the end unless the operator itself had mercy and cut down the payment.