two boosts is very difficult atm. without life orb boosting damage output pre-mega its wea af and can almost never stay nonmega if it wants to hit hard at all. and what bulky waters does this thing break as adamant that it cant as jolly, im curious, cuz neither set 3hkoes pert and neither one breaks cune either way,,,
I might be biased because I run Sharpedo on a hazards team, but there are some significant differences...
First, against Suicune, the 3HKO is very important, because if you outspeed, a 3HKO means you can kill it while it's resting if you don't get burned by a Sleep Talk Scald. Jolly misses that (only a 19% chance to 3HKO), which is pretty huge, considering how common Suicune is.
Second, with rocks and a layer of Spikes, Adamant Sharpedo has the guaranteed 2HKO on Swampert, but Jolly does not.
Third, there are threats such as Mega-Blastoise where 2HKOing them is as good as losing to them entirely, because they can OHKO you with Aura Sphere or whatever. If I want to sweep with Sharpedo, I need to make sure that Blastoise is worn down to OHKO range first. For Adamant, if it switches in twice with rocks and a single layer of Spikes down, it's in OHKO range from Crunch. For Jolly, you'll need some additional damage.
As for getting two boosts, it basically means bringing in Sharpedo on something it can revenge kill or chase out without needing to evolve. I've got several replays of me doing exactly that; I'll track them down and edit them in.
Finally, the other main reason to go Jolly over Adamant would be outspeeding Hydreigon, which is admittedly nice... except that as Jolly, you only have a 6% chance to OHKO Hydreigon after rocks damage.
I guess some of this stuff is team specific; I'm not trying to say that you should never go Jolly (although I guess my last post kind of implied exactly that... sorry). But I tested both out on my team, and going Adamant made a pretty big difference for me.