I'm still open minded on this topic, however I tend to agree with monbla. I prefer the wider bowl for two reasons.
First, it does make your tobacco more full flavored, even though with flakes you are usually burning a very small area of tobacco in the bowl, especially during the first half of the bowl. This factor in itself should tell you that the internal shape of the bowl is affecting the flavor. Some folks believe wider bowls taste different because you can light more tobacco at once, but I don't believe this theory, especially when smoking flakes. The goal should be to have your tobacco barely lit for maximum flavor, not to set as much of the tobacco on fire as you possibly can.
Second reason I don't like tall narrow bowls for flake tobacco is because by the time you reach the bottom third of the bowl, some blends get too soggy to light and finish smoking. Then you need to give the pipe and tobacco a couple days to dry out, before it is enjoyable to finish.
I have a really small pickaxe pipe that was destined for flakes according to the pipe geometry police. Internally, the bowl is three times as tall as it is wide, so I dedicated it to FVF exclusively. Does it deliver superior flavor compared to my wider bowled pipes? Not that I can tell.