Once benchmarking was complete, I forced the browser to garbage collect the memory in each extension by clicking the trash icon (in the dev console) a couple of times. These screenshots show the memory footprint of Adblock Plus (ABP) and uBlock Origin (uBO) after they have gone through this demanding benchmark. Benchmarks were performed on Linux Mint 64-bit using Chromium. Each extension was tested alone, with no other extensions enabled. Here is a quick illustrated comparison of efficiency using various angles. Still, in recent benchmarks, uBO still comes out as the most efficient memory- and CPU-wise when compared to content blockers with similar set of features and capabilities.

The code base of all content blockers have undergone significant changes since then. Note: The data presented in this page were collated in 2015, so they shouldn't be considered up to date (the section Added memory footprint to web pages is still relevant though).