Ok final conclusion:
Blades have higher accuracy: +112, compared to +105 attack accuracy for the Saradomin sword. They require only 60 attack to be wielded, unlike the sara sword which requires 70 attack (and no strength level for either weapons).
The sara sword provides +3 prayer bonus, blades don't have any, but blades give +4 more strength bonus, giving you 1 extra max hit compared to SS with full gear.
Blades have the same special attack (different visuals, and i think it hits a bit faster than SS special), but it hits higher on the first hit (6 more max with full gear).
Blades are much slower than the SS though, compared to 2h speed, and SS has the same speed as a whip.