Unlock Gear is the most important for your first few prestiges, especially depending on what game modes you play. It doesn't just offer weapons - perks and equipment are there, too. A lot of search players rely on Dead Silence, and having that ready to go at level 4 instead of 55 can make a huge impact. Steady Aim is great for the SMG lovers. Portable Radar, C4, and Tactical Insertion are highly valued equipment. Selecting a weapon you know works for you on top of a few "go to" perks and equipment make prestiging not that big of a deal, compared to previous games where you'd have to suffer for hours until you feel whole again. That feeling, enjoying the fact you prestiged instead of hating it, to me makes the Unlock Gear choice the best choice.
After that, for sure Extra Custom Class. While 5 is enough to get by, tricks like making a duplicate class so you can switch back and forth to bank up unused killstreaks is invaluable. Being forced to call them in or else lose them is a nuisance during intense matches where you aren't going to roll over your streak multiple times. I've unlocked all 10 and use every one without feeling like there are too many. SMG rushing, Shotgun, two sniping variants, one AR with a duplicate copy for killsteak banking, anti-air support, s&d, and a specialist loadout for a solid 9 that I can always rely on. The 10th is arguably a waste as a riot shield, but that is for my own enjoyment and thus, not a loss.
Double XP flies by for the reasons stated above. A double XP weekend is going to benefit you far more. As for the titles and emblems, if you really want them, save them for last. They aren't very unique - many people sport them and they don't make you stand out in a crowd.
