Honestly, the pro or pro2 has one of the fastest wake up times. its so fast that even waking up after hibernation is just as fast as sleep. but letting your device hibernate more vs. sleep would improve battery life. you can go into each power profile settings and adjust how you want the device to act. like when you press power button. if you want it to sleep or hibernate. but technically, its supposed to wake up faster from sleep.
Because you are writing to the SSD. If you set your device to hibernate quickly, that will increase the number of times it writes to the solid state drive. Personally I doubt that would be a significant issue for most users, but if you want the maximum life from your device, (long past the point it becomes obsolete) then hibernating would not be a gone thing to do multiple times a day.
Hibernate writes the contents of RAM plus the Page file to a file called hibernate.Sys, it is the size of RAM and Page file so on an 8GB machine it could be as large as 20GB (8GB RAM + 12GB Page File).
I see (re:hidden). As for why sleep takes longer to wake up than hibernate if you leave it for a long time... Yeah, I have no idea. I leave my Surface 2 on sleep overnight and it still wakes up instantly (though really I should have shut it down).