Hmm.. Well, I just found this page from a google search. It's one guy's word, but he is authoritatively stating my suspicion.

http://robosavvy.com/forum/viewtopic.php?t=9655

"Myth 3: ABS is much stronger than PLA
This is the most recurring one and it's also the most inaccurate: if you compare injection molded parts, ABS parts are indeed stronger than it's PLA counterparts; however we're doing 3D Printing layer by layer, not injection molding and this changes things considerably:

A 3D printed part in PLA is MUCH stronger than a part printed in ABS. This is because PLA has significantly stronger layer bonding than ABS."

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I'm going to start looking at other filaments. But would any of them be an improvement? Maybe inserting metal pins is the way to go. Edit: Cool, jimc, I will look into that!