Contrary to the popular belief Kabuto's involvement had more disadvantages than advantages.
Obito would've won the war, Think about it. No Kabuto means >> no Edo Tensie >> no Edo Itachi >> no Sasuke turning sides >> no Orochimaru >> no Edo Hokage.
Sasuke would be fighting Naruto, while Obito already took care of the rest of the shinobi alliance via Transforming Zetsu's into Alliance members and assassinating them.
There would be following Match ups:
Sasuke vs Naruto = Stalemate
Obito with Six paths and Gedo Mazo vs Gokage = Obito stomps, since none of the them have counter to Kamui.
100,000 Zetsu Army vs 50,000 Alliance = Half of the alliance army was wiped in 1st day, with Zetsu Assassinations we can also call this a stalemate.
Obito's strategy was simple He wanted to grab Naruto when he is exhausted so he can take out the Nine tails and become Juubi Jin.
IMPORTANT: Obito is the only person in Narutoverse to move around the world within seconds via teleportation. He could easily swap through battlefields causing Havoc while finally sneaking behind Naruto at a critical moment in his fight with sasuke to absorb him....Take him to the other end of the world >> Extract nine tails >> Summon Gedo >> Become Juubito....G FKIN G