Differences between PS3 and PS4 besides graphics?

[Kosmos992k]

the PS4 HD is still 5400 RPM <<. Infact I got one out infront of me that I had replaced with a 99$ 1tb Hybrid a year back.

It's acceptable, not great.

And as I said, "Yes an SSD will improve things a bit, but it's not like the PS4 is suffering long load times."

5400rpm standard 3.5-inch sata laptop drive, yes, I know.

3 things will make any system with a 5400rpm drive faster.

larger cache on the disc controller
higher RPM (risks more noise, more power used, and some additional heat)
SSD/Hybrid (though historically the better models of these are more expensive and smaller than equivalent HDDs).

However, unless the acceptable performance of the PS4 is a problem, you're spending money to fix something that's not broken.

I have to say though that I will more than likely upgrade the HDD in my PS4 at some point when I want more capacity, and will look for a faster option than a 5400rpm. If I'm already at the point of upgrading there is no reason not to upgrade performance as well.