I've looked over both Swordsage and Warblade, and also looked over the abilities.
The difference in BAB is made up for in their maneuvers/stances known/readied ratios.
When it comes down to the abilities it's..
Evasion vs Uncanny Dodge
Disciple Focus vs Battle Skill
Dual Boost vs Stance Mastery
Then on the Swordsage's side there's Quick to Act +1/2/3/4/5, AC Bonus, and Sense Magic
Warblade has Battle Clarity, Weapon Aptitude(Which is duplicated by one of the Disciplines), Battle Ardor, Battle Mastery, and Bonus Feats.
The Discipline for Dual Wielding seems to be Tiger Claw, which both have access to.
Warblade has Iron Heart and White Raven, Swordsage does not.
Swordsage has Shadow Hand, Desert Wind, and Setting Sun. Warblade does not.
Where one lacks, the other seems to take up the slack.