you can use both together
but if yur comparing a pelt + aircooling
to just water cooling without pelt then i would say it depends (on the quality of the cooling and the number of and wattage rating of the pelts)
if you want the ultimate then use pelt + water cooling, vapochill, or something like that
i would say running a pelt is risky if yur gonna be using it in yur system all the time because they can fail and then become insulators of heat, destroying everything. If yur gonna be using air cooling just get a good hsf and forget pelts
if yur looking for great "extreme" cooling use water cooling (need a water block, pump, and radiator)
if you want a "super cooled" system then use pelts and water cooling
a peltier itself cannot cool, it basically just sucks heat and spits it out and then some
so you need good cooling on top (ie: water block)
you use pelts to go below ambient temps or even subzero
you have to be carefull tho
read up on everything first, there is a lot to be carefull with
if you get any farther then come back and people can answer questions
have fun
--Soul_keeper