i think the reason that direct comparison between the different ergon products are hard to find is because most people only have experience with the product that they eventually bought.

i bought GC3s for my hybrid last summer and i instantly fell in love with them. i've always placed a premium on multiple hand positions, so the GC3s were the natural choice for me.

as for plugs in carbon bars, that i don't know about as i have an aluminum flat bar.