You're asking the wrong question. For starters, you're asking between Android (an operating system) and iPhone (a piece of hardware). But even if I ignore that, you're asking about phones. I always consider phones insecure, and I don't trust them. It's great for keeping a small amount to buy coffee on the road, but if you want to store any serious amount, get a Trezor hardware wallet and learn how to keep it safe.
It's helpful because I was also searching for the same questions, which help me in the long run for keeping my bitcoins secure, but here I have one question currently I am not able to have a Trezor hardware wallet, but I am using a desktop. Can
I secure my bitcoins for a long time without any problem?
After doing some work and having a search, I feel Electrum is best for newbies because it's easy to use and also has good features, but a seed or phrase is a problem in case of loss; it's not easy to recover just because of this. Asking before starting,
I want to have a few good suggestions. I mean, can I start with Electrum, or first I have a Trezor hardware wallet and then go ahead with my savings in Bitcoin?