Also depends heavily on the algorithm being used, newer zram algorithms are much more efficient than the old ones used in stockThat's a good question. I have read both sides to the story. Some people say it speeds up there phone and others say it slows there phone down and drains battery life. I have to say when I enabled Zram, it would slow the Lgv20 phone down that's for sure. I think what it comes down to is Zram only works if it's optimized for the phone. I optimized Zram for the Lgv20 phone to only use so much ram and no more than half of the available ram, we have about 1.8gig's to use. I think I am getting better battery life because we have more ram and we are using the eMMC drive a lot less.
So it all depends if Zram is optimized for your phone or not. I would have to say most phones it's not optimized and that's why people don't like it.