I've killed a couple of FSA MegaExo bottom brackets. Neither lasted 3500 miles. That was years ago, so they may have fixed whatever problem was causing that.

I've had both Gossamer and CX50 cranksets. Neither is anything special, but I never saw anything wrong with either one.

You say you can get the Gossamer for $75 cheaper than the CX50, but I would think that must be a particular closeout deal and you won't be able to specify the bottom bracket that you need. You can get a CX50 crankset for under $100: https://www.universalcycles.com/shop...4&category=521

You can get it even cheaper if you're willing to order from a UK website. The Shimano bottom bracket you'd need sells for about $20 more.

BTW, you probably know this, but replacing the small ring with a 34T is cheap and easy.