FedEx is a bunch of different airlines...
777 is 99% international. Lots of 24/36 or more layovers around the globe. But you cross a lot of timezones...
757 Germany is mostly night ops...2 -4 legs a night.
767 HKG is 70/30 night day, with some 24/36 layovers. (I am a HKG 767 Captain....)
MD11 ANC is largely international, as is LAX. Not many vacancies. MD11 MEM is a mix of everything....very dynamic bid pack.
A300/MEM 757 are day/night domestic ops. Lots of good flying. Lots of night flying. Guess which you'll get when you are junior?
When I weight decision, here are some considerations I'd consider:
Pay rates and fleet types. Delta pay rates are great, but you can probably get a WB sooner and for a great percentage of your career at FedEx....
Domiciles verses commuting. If you like or can get to ATL, NYC, SLC, DTW with ease you can certainly maximize your quality of life. If you like living in MEM, HKG, CGN....or perhaps ANC or IND you can have a good life here too. If you are going to commute, FedEx schedules and DH pairings probably make it an easier and less stressful option...
Non reving. How important is it to your family? I make enough at FedEx to buy tickets, but my AA and DAL counselors all have very happy wives who bounce around the country and world with ease. They have to watch loads, plan trips, etc but it does seem (outside looking in...) like a good perk to have. Wife hate to fly or travel? FedEx is not such a loss. Wants to go all over? Hmmm..there may be some value in doing the pax thing.
Retirement? Yeah...we got a 130k pension. I think it can be improved outside section 6, but the price would likely be the removal of an A plan for future hires. That decision will be made above my pay grade by our union reps, and there are pros and cons both ways. A few green slip trips invested in a 401k or outside account may not quite match that pension, but I think a smart guy with 20+ years at Delta should be able to do quite well if they manage their money effectively.
I suggest you take a look at both carefully, then realize whatever you do there are people who would kill to have either job. You won't be "wrong" either way. With that in mind, throw a coin and call heads or tails. When the coin in the air, ask yourself what you hope it lands on....and that is probably where you need to be.
I'd give the edge to FedEx for first few years for money. I'd give the edge to Delta for comfort and quality of life (avoiding backside of clock flying). Once you can hold some day flying or carve your niche at FedEx is tends to be less block hours and some great benefits. But...yeah...every once in a while even a senior guy gets to suck up a tough trip. You don't want to go to work for 5 years hating the job waiting to finally get that trip/layover you want. You better enjoy the job as you go along or its just going to be miserable.
Great people at both places....good luck whatever you do...