Long wide blades which are swung fast inevitably experience times when they stall during quick redirections, this can be felt and it definitely slows the blade down and reduces control. The ability of a blade to handle an increase in the angle of attack of 30% is a big advantage as the blade will turn much more quickly. It will also help to reduce the speed inefficiency caused by misalignment during a cut. This won't be felt anywhere near as much with narrow more thrust orientated blades, nor will it be noticed as much in dealing with a single opponent, when compared with the more continuous circular movements required for control of a 360 degree area. Wide thin cutting blades are just like wings with very low chord ratios in that they only accept a narrow range of angles of attack. Wide cutting blades have very low chord ratios around 6 percent, making high speed maneuverabilty a definite issue. In broad terms the undulations can increase overall efficiency by up to 20 percent, that's a huge increase and would not only be felt in increased speed and maneuverability but also as less of an energy drain on the wielder of the sword, which could be significant during long battles. The fact that the sword undulations have rounded sine curve like tips rather than pointed serrations also points to aerodynamic efficiency as the goal rather than the 'bread knife' cutting effect sometimes put forward as their reason for being. By the way it's also the case that blades with spatulate tips generate much less tip drag than pointed blades. Tip vorteces contribute a large proportion of the overall drag produced by a wing. So, in addition to giving the sword a longer cutting reach, the spatulate tip reduces drag and thus increases blade speed. This is even more the case because the tip is the part of the blade which is travelling the fastest and thus produces proportionally the most aerodynamic drag. As has been noted countless times by RMA practictioners and ARMA scholars, sword makers were far more knowledgable than has been commonly supposed in recent times, and in my opinion the undulating blades are another example of their enlightened creativity and practicality.