Yes, you can take a photo while on a call. No, you can't record a video while on a phone call. While we aren't Apple here on this user to user only forum and we can't speak for Apple, this is likely due to the high processing requirements of being on a phone call and also trying to record a video at the same time. That would logically push the battery beyond it's normal operating limit.
If you want to move to another device, that certainly doesn't matter to anyone here. But be advised, I just did a search and found that you can't do this on an Android either. But sure, get whatever you think better meets your needs.
It has always been this way, but you can certainly let Apple know you'd like this capability (though they likely won't be able to give it to you) here --> Feedback - iPhone - Apple