Top equitation trainer Missy Clark explains the difference between padded and plain saddle flaps, and their uses. From Practical Horseman magazine.
My show-ring motto is "If you notice it, it's wrong." I don't think equitation judges notice which type of saddle flap you have unless it's really obvious--for instance, a big, bulky knee roll, or a flap that fits you poorly.
The amount of knee-roll support you need depends on how secure your leg position is. A flatter, more streamlined saddle flap shows off a nicely positioned leg. A flap with a slightly more built-up knee roll (one that has a supportive leather block sewn into the skirt under the flap) helps your leg stay in the correct place.
If you're a novice, I have no problem with your using a modified knee roll with padding under the knee and a block (although not too large) under the flap-but with the goal of being able to use increasingly streamlined flaps. As your leg position grows stronger and more independent, you'll eventually prefer the feel of a flap without extra support.
More experienced riders may still use suede or "pillow" knee rolls, which are quite attractive and perfectly acceptable--but I'd want them to avoid bulky blocks sewn into the skirt. If your saddle has blocks that you think you can do without, you can ask a saddler to remove them--or you can cut them out yourself (carefully!) with a seam-ripper.
Top equitation trainer Missy Clark explains the difference between padded and plain saddle flaps, and their uses.
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