Powder burning speed is somewhat ambiguous characteristic. Powder burning occurs on surface of its pieces, and the surface area changes over time. For spherical powders the surface area is diminishing with the burning, as radus of the burning balls goes down. For flake powders, which have pieces like washers, the diminishing is much less than for spherical. Dynamics of the powder burning is described in the "vivacity curve", which basically tells what percentage of the powder is burned over a given time under controlled conditions.
Considering the above, last pieces of a spherical powder burn slowly than of a flake powder. If you rank powders by speed when they burn completely, flake powders go higher in the rate. If you rank them by speed when, say, 90% of the given powder burns under the same controlled conditions, then spherical powders will go higher in the list.
The two powders have different shapes of the vivacity curves. You may see from the above how these two may be ranked differently in rate charts.
Back to practical part of your question. I also use Red Dot fro 9mm loads, as many others in this thread. It burns clean. The measuring, however, in tiny 9mm dozes is a bit challenging. I have made a mod to my disk measure to have a reliable drop under 3 grains.
Here is the picture.
