different voice coil configuration...no real ups or downs of either, it really depends on what amp, how many speakers you want to use, etc.
2 ohm will be less resistence and ask for more current usually resulting in more power to your speakers.
less resistance=more current=more watts (compared to 4) remember to keep this in mind when getting any audio equipment, it can mess up your math if you don't watch the impedance on all components. also generally the lower ohm's are better equipment.
What about 1 ohm? if i wire two subs down to 1 ohm. isnt that to supply a max amount of watts to two subs?
jonnys right, if you wire up subs at 1 ohm to an amp that is not stable to 1 ohm it will shut down and maybe cause damage. Also it will put more stress on your alternator and battery.