Anyone who has any experience programming and working on both Android and iOS apps can tell you that there are most certainly malicious apps on the Play store. Here's the deal:
In order to publish your app to Apple's App store you have to submit it to Apple for review. Oh, and you also have to pay them $99 per year and jump through some other hoops. Either way, Apple goes through your app's code line by line (or at least that's what they claim) and verify there is not malicious code. As a lot of devs can tell you, it's not hard to get an app rejected and not all that uncommon to have to resubmit. The end result is that the Apple App Store is about as safe as it gets. Not perfect, but as far as safety it doesn't get much safer.
Now, if I develop and app for Android I can basically just upload it to the Play Store. I will need to create a developer account, but that's all I have to do. If my app contains known viruses or malware Google will eventually catch it and remove it from the app store.
The important thing to keep in mind about Android is that it really is closer to Windows in that you can easily mess around and download an app or apps that can steal your personal information, slow your system down due to poor design or ads, and any number of other things. My best advice is to pay very close attention to an apps permissions and if in doubt just don't install it. Also, even if you don't usually read reviews on iOS devices, I would recommend that you at least take a look at the reviews for any lesser known Android app you are considering installing. You can find out pretty quickly if the app has been causing other users problems with their devices.
For this reason, I would not recommend just indiscriminately downloading every single app that looks interesting on Android. You really should be savvy enough to pay attention and protect yourself. In addition to programming I have also worked for a few years in the mobile industry and I can tell that I hated to see older users get Androids because they would end up with so much crap on their phone and then wonder why it didn't work the way they wanted. If this is you, then you maybe you should go with Apple. If you don't mind paying attention to what you are doing then Android will treat you very well! Hope this helps.