I don't think that there would be any real hinderance if you are already used to the triangle shape. I would assume that the surface texture would matter more.
The only triangular pen experience was with a
Staedtler Triplus. When I started doing more top spin tricks (Shadow, Neobackaround, Backaround 1.5, etc...) I found that the surface texture was the main deterant to further using the pen.
A triangular pen with a smooth surface would be great for top spins, the shape itself also seemed to be easier to hold for Sonics and similar tricks.
It's been quite a while since I've last used such a pen, but I can't immediately think of a reason why you want to change just because of the shape. If you are happy with what you are currently using, keep going with it until you tire of it or find/try something better.
Edit: moved thread out of the main forum into the Pen Discussion forum.