your 2nd one must be wrong, because it can't deal more than the mega. life orb gives *1.3. see my previous post.
oh i forgot about tough claws again, head smash(?) and brave bird get boosted... meaero would die fast but damn would it be stong... so probably still better than normal aero :P (although, who says you can't use both? change to megaero if in need of more power, otherwise just spam recoil-less really strong STAB moves...)
Did some others to check.
Normal Aero
252+ Atk Life Orb Aerodactyl Stone Edge vs. 252 HP / 252+ Def Forretress: 114-136 (32.2 - 38.41%) -- 99.85% chance to 3HKO after Stealth Rock
252+ Atk Life Orb Aerodactyl Head Smash vs. 252 HP / 252+ Def Forretress: 172-203 (48.58 - 57.34%) -- guaranteed 2HKO after Stealth Rock
252+ Atk Choice Band Aerodactyl Head Smash vs. 252 HP / 252+ Def Forretress: 235-277 (66.38 - 78.24%) -- guaranteed 2HKO after Stealth Rock
Mega
252+ Atk Aerodactyl Stone Edge vs. 252 HP / 252+ Def Forretress: 105-124 (29.66 - 35.02%) -- 34.72% chance to 3HKO after Stealth Rock without Tough Claws (not sure how to fake factor them in)
Now factoring in Speed for normal:
Adamant 252 EVs = 359
Jolly 252 EVs = 394
Mega Speed:
Adamant 252 EVs = 399
Jolly 252 EVs = 438
Mega will always be faster than Normal. But Aero hits harder assuming it gets Head Smash. If not:
252+ Atk Choice Band Aerodactyl Stone Edge vs. 252 HP / 252+ Def Forretress: 132-156 (37.28 - 44.06%) -- guaranteed 3HKO after Stealth Rock -- Normal
252+ Atk Aerodactyl Stone Edge vs. 252 HP / 252+ Def Forretress: 105-124 (29.66 - 35.02%) -- 34.72% chance to 3HKO after Stealth Rock -- Not factoring in Tough Claws