I've always felt that A10 was fishy when they never quote layer 7 performance, only layer 4. What are we still in the early 00s ? Pretty much everyone should be on layer 7 these days, and in most cases should probably use load balancer configurations that re-use http connections on the back end servers (F5 calls it oneconnect, forget what Citrix calls it - I think just connection multiplexing - and it's on by default on Netscaler - last I used F5 it wasn't on by default but not hard to enable). From what I was told this particular technology was created by Netscaler, and then cross licensed to F5 (in exchange for F5's cookie handling stuff).
Layer 4 load balancing was more useful back in the day when the code couldn't leverage more than a single cpu core. I remember back with BigIP 6400 I think it was - several years ago dual socket beefy systems, but only 1 cpu could be used for load balancing (we used the other CPU for global DNS). Nowadays, even though the code isn't *that* good, it's good enough to run on multiple cpus, hence crank up a few more features and deliver a better experience to the end users as well as to the back end servers.
layer 4 I suppose is fine for non HTTP/HTTPS protocols.
A10 does do Layer 7, but for some reason I've never - ever seen them quote performance numbers.
I used F5 for a long time, though past couple years have been using Citrix to see how it works.