As someone suggested, I'd have to say look for the one with the most CCA and you'll be much better that the OE battery that come with the P5.
As for how long it is really depends on how much power you're drawing from it (ie. amps, speakers, accessories such as neons, ect..) If you're not running any EXTRA per say you should be OK to get a long life outta ur battery. If you're into performance and have the heavy pounding system setup (ICE) then you wanna make sure that you have th battery power to support it. Optima red-top's are good for an improvement over the OE but if you're really need a performance battery go with the yellow-top. You will notice a drastic difference, again, if you're running all the accessories, ie. your lights won't dim as much at each strike of that deep bass.
Hope this helps!