A microbenchmark like this is not very conclusive. The G1 collector is designed to handle the heap fragmentation problem and thus reduce the maximum pause time due to stop-the-world GC. It's not designed for maximum throughput.

Each GC algorithm has its worst-case behavior; saying "avoid at all costs" because of a single scenario is not very helpful.

Also, what were the JVM flags for each test? All I can see in these graphs is the bump at the beginning before the heap has sized to a stable level.