I use both Android and iOS. IMO neither is inherently more unsecure, provided you use a little common sense. They both have pros and cons.
iOS is great if you want Apple to tell you how to use your device and to give you little room to customize anything. But as a result it may be a bit more reliable. Android gives you way more flexibility, but of course can be riskier if you are not careful.
As I noted earlier, I have several cheap pre-paid Android phones (that I pull the SIM cards out) that I use for all of my solar monitoring needs (including remote monitoring). I can do things with those Android phones, that I can not do with an iPhone (or at least not as easily, and certainly not as cheaply).