Many sources you find will tell you that bavette is simply the French word for flank steak. However, they are actually slightly different cuts although they are from the same part of the cow and have many similarities. I asked my butcher about the variances, and he explained that bavette is a little bigger and that the fibres in the meat are both longitudinal and transversal. A little technical I know, so I had to try and work out exactly what this meant in terms of taste and texture.
In the spirit of testing, I bought both cuts to see if I could discern a difference in taste or texture once cooked. The fibres in bavette steak are looser and seem almost deeper, making the cut less dense. Bavette is also a more tender piece of meat (compared to a flank prepared and cooked in the exact same way).