Reinforced paper cones seems to be one of optimal choices, dont know to which extend slicing the paper etc. is just hype... ?
low-end would be poly-propylene materials... it has a smoother and deeper (comparable to paper), but clearity and precision is very bad - PP simply flexes too much when playing bass, making distortion the rule rather than the exception. Surprisingly many manufactures markets their pp cone woofer as quality - showing of their smooth response curves and low-end fs values... and only very very few gives you any idea of rated distortion and power compression, which is much more important in a bass unit.
from what I've heard aluminium is not optimal when it comes to timbre, i.e. it makes the sound less natural, and Kevlar tend to have a less uniform response curve than paper, but have a deeper fs value, ideal for non-vented enclosures, but who uses that for bass?
Anyways the point being that its a trade off (between many things, where paper still seems to posses the best of each.
I myself have two 15" paper cones - one $50 that sounds like crap compared to my $500 JBL 2226 G 15", but that would be expected - paper cones comes in many varities too...
A.