Well in Naruto Orochimaru had not 'perfected Edo Tensei whereas Kabuto now has. That is also why Hashirama and Tobirama were not at full strength when they faced Hiruzen but are at full or nearly full strength now.
i think they are at like 75% now... since tobirama was unable to free himself..i bet if they were brought back at 100% like madara, he would have been able to.