Sasuke's Losses:
1.Advanced Healing Factor:
After absorbing Orochimaru into his consciousness, Sasuke recovered from his injuries alot sooner (Similar to Naruto). He was also capable of using Orchimaru's Body Shedding technique to repair any damage done to him during battle (As seen during his clash with Itachi), at the cost of a large portion of his Chakra.
2. Snake Techniques:
Sasuke was seen using quite a few snake techniques prior to his final battle with Itachi (even replacing his lost wing in CS2 with snakes during his battle with Deidara), and while most people assumed that he'd signed a contract with them, it was never confirmed in the manga. Therefore, the only theory that could be made is that his summoning of snakes to aid him in combat was due to having absorbed Orchimaru.
3. Cursed Seal Of Heaven:
Well, this is clearly the most obvious. Sasuke is no longer capable of transforming through the use of the Cursed Seal, and has lost the power boost that comes along with it (Not that it's even an issue anymore since he's awakened his Eternal Mangekyo Sharingan).
Gaara's Losses:
1. One-Tailed Beast [Shukaku]:
Gaara mainly lost his tailed beast; and with it, any form of stamina, chakra, and power that it contributed to his manipulation of Sand. He is also incapable of transforming into his One-Tailed State. However, Gaara still maintains his ability to manipulate sand, on an even greater level than he could while Shukaku was still sealed inside him.
