I've researched this for my children, and there seemed to be significant differences. The amount of superstition in the Steiner teachings put me off big time ("Beware of right angles and potatoes!"). Montessori makes far fewer wild assumptions.
If I had to pick a single strength of Steiner education, it would be that it genuinely believes that traditional academic skills aren't the only skills worth having. Lots of guff is spouted elsewhere along these lines, but at Steiner school people who were good at sport or art or whatever were genuinely just as valued as geniuses in writing and maths, which gave the place a lovely ethos.
Can you elaborate more on this?