Car Subwoofer 4ohms or 2ohms?

I have this amp (http://www.crutchfield.com/p_500MRP1000/Alpine-MRP-M1000.html?tp=115) and bought 2 subs that don't fit my box so instead of getting a new box I'm switching the subs. The sub I'm getting comes in 2 ohm (http://www.crutchfield.com/s_20609S10C2/Kicker-Solo-Classic-09S10C2.html?search=solo+classic+s10c) and 4 ohm (http://www.crutchfield.com/s_20609S10C4/Kicker-Solo-Classic-09S10C4.html?search=solo+classic+s10c). Which one would work better with that amp and why?