The real answer is not that you are getting better performance. It's that you simply aren't as aware of how those heavy games are actually supposed to look like running at full speed so they look "good enough" to you when in reality, they are chugging, lagging, etc..
No that's not it, considering there are clear differences that can be visually perceived.
@Crush I can't think of any reason for that. Actually, a network storage would add some delay when loading data compared to a local storage.
Having such an immensely complex system like RetroPie and its underlying Linux OS makes comparisons very difficult, as long as not everyone has a freshly installed system from the same image with the same peripheral hardware and settings. Picking one prominent difference is not much more than a wild guess.
That said, which "heavy games" are we talking about exactly? And how do you compare your system's performance to those of others?
Thanks for that explanation, makes sense, I kinda wondered if maybe somehow it took of some of the load of handling the storage, but I'm guessing that's not possible then.
It's mainly Dreamcast/Atomiswave/Naomi games, where some get stuttering while i don't, most notably in Marvel vs. Capcom 2 on Naomi, whilst on Dreamcast it stutters for me as well.
"as long as not everyone has a freshly installed system from the same image with the same peripheral hardware and settings. Picking one prominent difference is not much more than a wild guess."
You've hit the nail on the head with that.