annother newbie ? liners, Polyethylene vs EPDM

I've been checking out prices for liners (mainly online) and i've noticed
that the polyethylene are usally about half the price of the EPDM, which
means i could build a pond about twice as big... the warranties on both are
for 20 years, but it seems like people usually buy the EPDM. Has anyone out
there had experience with the polyethylene liners, or know of any major cons
to it? obviously i'd like to build the biggest pond i can without having to
spend more money, but i also don't want to have to replace the liner later
on. any ideas? thanks!

Megan