Overall I’ld expect EndlessOS to be more ressource hungry. It is build for 64-bit and the whole desktop is way nicer and has more effects than LXDE.
IÄld say it depends a bit on what you want to do with it. I am using endless on a 11 inch convertible laptop with a touchscreen and it runs on a 1,1 Ghz Celeron with 4GB Ram and 128 GB SSD. Everything runs smooth and flawless, I can watch videos in FullHD without problems and even Steam In-Home Streaming works (maybe a few glitches in the colors but that could be connection related). So I have pretty low specs already and Endless just runs fine. I wouldnt want to trade it with LXDE since touchscreen support would prolly be a disaster.
If you laptop is 32-bit I think you have no choice than to go with LXDE, cause for the 64-bit EndlessOS I’ld recommend 4 GB of RAM. You can try it with 2 GB tho, it is not that RAM hungry. If you have 4 GB tho and your laptop is a 1,xx Ghz somewhat, you will be perfectly fine with EndlessOS. If you plan on using ur NVIDIA or ATI gfx card, it wont work; endless is more for browsing and office use than gaming (except In-Home Streaming for that its just perfect).
I am pretty happy with the system for work purposes, surfing in the garden or In-Home Streaming. I use the little laptop more often than my main laptop running Ubuntu. If you want to upgrade yourself one day, I can recommend the Acer Travelmate Spin B1 with Endless OS. It comes pre-installed and everything works just out-of-the-box.
Greetings,
~ent