I don't think how often you save really effects difficulty all that much. Even if you could save at any point you wanted to, that doesn't make the game any easier.
I admit, I use save states when I play games on the computer. No it doesn't make the gameplay that much easier. It doesn't make it easier to kill a boss. It doesn't make it easier to find items. All it does is let you save and that's it.
That's something I hate about games today. I feel games should allow the player to save at any point. This is something I did not like about the Metroid Prime games and Metroid Other M. There are times, when playing those games, that I'm tired or I need to go somewhere. I can't just shut the game off; I'd lose progress, so I have to hunt around for a save station and sometimes the nearest one is a good distance away and I have to fight enemies along the way.
I was relieved when I found I could save Metroid, Metroid II, Metroid Fusion, and Super Metroid at any point since I play them on the computer, not the consoles themselves. It didn't make the gameplay for any of them any easier. I still died. But being able to save at any point, even in the middle of a boss battle, was a great improvement, in my opinion, as it lets me stop playing at any moment.
