The advantage of cerowrt is that it runs about 3-4 months ahead of openwrt on improvements to the bloat problem, and fixing bugs.
The disadvantage is that it runs about 3-4 months ahead of openwrt on having new bugs.
Example: We just finished (with the aid of multiple parties ) finally fixing a problem in HTB's atm DSL compensation that has existed for a year (and probably several years before that), and I think the final set of fixes will land in Linux 3.10.10 or .11 soon.
Right now it's very possible to merely layer two components of cero on top of openwrt to get most of the benefit of the current work. (the aqm-scripts and gui, and if you are daring, a couple patches to codel and fq_codel)
Sadly, I wouldn't recomend the current dev builds of cero for day-to-day use at this point, although I hope to get to a new stable release by the end of september. There's a ton of outstanding bugs left to fix.
While openwrt runs fq_codel by default on all interfaces, it's mildly premature to be doing so on the wifi front. Work is in progress. However in the general case, at the moment the principal use for fq_codel in a home router is on the gateway to the internet - the fq_codel QoS system in openwrt and dd-wrt works extremely well (with the exception of ipv6 native). I believe the package in cerowrt is better in most respects (notably on ipv6), but limited in others. Gargoyle is using a prior effort (improved sfq + an automatic rate measurement system called ACC). There are other options like using small atom boxes, ipfire, and several commercial products....