I've compared using Locust to Gatling and the only downside is that Locust wasn't able to reach the same RPS I was getting with Gatling. It's a shame because Locust is much nicer to work with in comparison.
That's hardly an issue as you can trivially build multi machine swarms with Locust.
Also, are you comparing a single Locust process to Gatling? Since Gatling runs on the JVM, it would be more fair to compare it to a Locust cluster with one locust process per processor core.