I was hoping for a quick trip to Vegas later in the year, but there seems to be little or no seats to LAX/LAS/SFO. Only seats to NYC, but then paying F miles for a J seat for the connection is not my idea of a bargain.

Anyway, I digress. The flight depends on you - if you can sleep in Y, then I'd take the long route. If you're restless, I'd take the NYC route and have a wander. I'd also look at a stopover for a day and have some time in NYC.

If the internal flight was on a narrow body I would also look at the longer flight - more room to get up and stretch. Also, you don't run the immigration delay lottery for your connecting flight.