It seems like everyone here like the 40Hz mode, and while I do agree it’s much better than 30fps, 45fps is where games start to feel like close to 60fps. It’s only difference of 5fps but it really goes from a better 30 to substitute 60.
I know 40fps has a frame time exactly halfway between 30 and 60, so I was expecting it to feel like it. But it’s not smooth enough to feel like 60fps.
I’ve seen 40fps content on YouTube on my 120Hz phone screen (no irregular frames then), as there are many displays of ps5 games running at 40fps. And yes, several videos did have a side by side comparison with 30fps and I could see a difference. I’ve tried 40fps on 40Hz on my Steam deck and it’s the same.
I’ve made the mistake of thinking 45-60fps was just 60fps locked, I’ve played several 60fps game in my time (and even 120fps, although rarely) and 45 is pretty close. I can only notice missing frames in a side by side comparison of 45 and 60, otherwise when you are in game paying attention you won’t notice it much.
The reason why folks suggest 40fps over 45 is because the Deck can reliably hit 40 in a much wider variety of games. 45 is a better experience, but it’s harder to reach in most games.
This is true, I don’t doubt it’s harder to get a locked out mostly locked 45fps compared to 40. But 45 looks much better with only a relatively minor increase in FPS.