Running a game made with U4 on "old" machines?

I was talking about this matter on this forum and somewhere else and getting contradictory opinions.
The question is whether a game developed on U4 would run both smoothly and nice looking on a machine with low range or mid range hardware.
I heard about scalability but yet I’m not convinced of what would be the final result. Do you think for old machines a project made with Unreal engine 3 at mid/high settings would run and look better than if made with Unreal 4 at low/extra low settings?
What’s your opinion? Anyone who has been experimenting with both engines?

Well I can max most UE3 games on my laptop but I am struggling to get over 24 FPS in any of the UE4 samples/tech demos.
I was playing around with the settings and even on 320x240, all effects disabled (that I could find commands for) some demos are unplayable.
On Cryengine 3 I have 30-45 fps on low/medium settings (same for Crysis 2) and thats enough for me to develop.
Unreal Engine 4 is unusable on this laptop, which is a bummer since I really looked foward to messing around with blueprints in non graphic intensive enroviments.
So to summarize, from my experience, UE 4 is only for more higher range hardware. At least I can’t get it to run anywhere near playable on an older set up.

What are you laptop hardware settings?

There are some post processing volume settings and world settings that really help or hurt performance. Also how you setup your lighting can really effect performance.

Thanks for the tip: i’ll take that into consideration