well i got to say = i bought the aksilver.. but well for me it's kinda crap.. i think i would be better whit the m4a1.. but it's totally the style u use to play...
i don't really know what my style is :P but it's just that u must be happy whit what u choose..
they are both the best :P just try 1.. and if it isn't the best 1 for u.. try the sim-card trick..so u can still buy the another 1 to :P