Itachi totally wins. Let's rewind to sick Itachi. Totally blind, coughing up blood, unable to function normally. Still uses Amaterasu and uses Susanoo, bodying Orochimaru and sealing him. The summoning animals could be easily sealed. The Totsuka Blade and Yasaka Beads are powerful enough to nullify Planetary Devastation. Almighty Push and Universal Pull won't be much use with Susanoo's shield. Also, Tsukiyomi is one of the most powerful dojutsu abilities ever. If Itachi can hit the Tsukiyomi, Nagato is FINISHED. He has one of the strongest genjutsu control in the entire series, and has beaten full-power jinchurikis on his own. And absorption of the ninjutsu isn't a problem, sine Itachi has a multitude of taijutsu and genjutsu. Itachi would win. Period.
I've got my ramen on the Akatsuki. The only real threats are Naruto, Bee, and Gaara. Itachi alone beat a jinchuriki at full power, and Nagato got that Rinnegan. Hidan and Kakuzu would be significantly harder to kill since the jinchuriki won't have the time and planning Shikamaru had. Also, the Akatsuki have Obito, who was strong even without the Juubi. In short, Akatsuki=Win. Gaara couldn't even beat the Second Tsuchikage (who is actually really strong) with Onoki's help, so I'm sure he could easily be defeated by Itachi, Nagato, or someone else.