CU HAS A HIGHER K VALUE AND IS LESS COSTLY TO BUY, THAT SAID NOW THE PRO FOR AL .  AL'S ARE MANY TIMES STRONGER AND COOL WELL EVEN IN A 2 ROW AND ARE ACTUALLY VERY EASY TO REPAIR ON THE TRAIL, CARRY TUBE AND CHAUKING GUN WITH YOU AND GET AL SEALER FROM YOUR RADIATOR SHOP [KIND OF LOOKS LIKE MARINE RTV, SETS FAST AND WILL GET YOU HOME, MOTORHD