Heh, I have broken both.
From my experience, yes, the 13mm rods are weaker than the stock pistons. I bent a couple of rods with some iffy gas and a little red mist once, the engine grenaded a few days later (presumably bent rods are on a short countdown to being broken rods).
Subsequent builds used H-beam rods and forged pistons. I never broke or bent a rod again, but I did damage a set of the pistons. And a very nice feature of a set of forged pistons isn't so much that they can withstand more abuse (they likely can) but that the failure mode is much more graceful. Instead of breaking, which quickly leads to rods and bock chunks flying out onto the road, they can (sometimes) just bend instead. Due (likely) to running short of fuel with a stock pump, I managed to shatter the rings and bend the upper ring lands on a set of Wiseco forged pistons. BUT: the engine did not blow up, all it did was start making lots of blowby and having low compression. Took it apart, put it back together with new pistons, a bit simpler and cheaper than starting over from scratch again with a new junkyard block.
Then I broke a wrist pin, and even drove it with a fair amount of vigor after I heard the ticking sound for the first time (it didn't sound very serious). The forged piston managed to hang together running 'one sided' while I did that, I'm pretty sure that a cast piston would have broken and I'd have scattered parts again.
Cliff notes: If you screw up and overstress the bottom end somehow, forged pistons are likely to help limit the damage.