I'm in a similar situation, having left a startup a year ago to work at $BIGCORP, naively thinking it would benefit my résumé. This is all painfully accurate.
The other thing about working for $BIGCORP is that it molds your skills to be hyper-specific to this company. It's less about learning to use cool technology stacks, than it is about learning the internal tools, procedures, and unspoken etiquette of the company. Skills that are vital to navigate the everyday complexity of $BIGCORP, but that you can't really export to any other job.
It probably will benefit your resume. At least that’s my experience.
Perhaps I’m too precious but economy class is awful compared to business class. Lie-flat seats are a significant improvement over economy. If you are spending your own money, sure, stick to economy so you can spend your money on other things that are more important to you… but someone else’s money? What conceivable reason is there to choose economy if someone else is paying.