In general, LOC is more forgiving for uneven workloads, especially for Ruby services. If a slow request hits, that machine gets less traffic than the others and gets some room to recover and burn off its queue.
Where we found weird problems was at the extremes: very low concurrency and exceptionally high concurrency.
Low concurrency meant that one host consistently had 2 connections and another consistently had 3. That's 50% more load on one host. I believe AWS has fixed this and now tie-breakers are resolved randomly, but it was kinda painful to deal with. Our solution was to scale vertically and run fewer hosts. 19 on one host vs 20 on another was less jarring.
The other extreme was 1k+ websocket connections per host. When we autoscaled, it would add a new host. That host would have 0 connections and so the next 1k connections would all go to the new host. For that system, we changed it back to round robin.