In 2016, I'd say speed was definitely a defining attribute. ag has very significant performance cliffs. You can see them in the blog post.
But as I mentioned in my comparison to qgrep elsewhere in the thread, everyone has different workloads. And for some workloads, perf differences might not matter. It really just depends. 900 KLOC isn't that big, and indeed, for simple queries pretty much any non-naive grep is going to chew through it very very quickly.
As for comparisons in other ways, at least for ag, it's on life support. I thought it was going to get removed from Debian, but it looks like someone rescued it: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=999962
The blog post also compares Unicode support, and contextualizes its performance. ag essentially has zero Unicode support. Unicode support isn't universally applicable of course---you may not care about it---but it satisfies your non-perf comparison criteria. :-)