Do you have anything to quantify "much, much worse"? From what I've seen they're roughly as bad as each other.

All I have are personal anecdotes, but I know I've had several Ruby scripts that have had to be scrapped/moved to other implementations and/or languages because MRI wasn't actually removing objects, even when the garbage collector was explicitly called, and thus became exponentially slower as the script ran, or because memory usage just gets out of control and the script gets killed by the OOM killer. I haven't had any Python scripts that have encountered these problems yet, despite doing the same or very similar things.