depends how your using it.... i dont think 2 mil will make a world of diffrence.... it would just make it stronger/more durrable ... as for how much its worth ... really depends on you . its only worth as much as people are willing to buy it for . if you mean how effective is it... im under the assumption it reflects 90% of light and should redirrect a considerable amount of light back onto your plants . light which otherwise would be wasted... if you need 150 ft of this stuff u either have a big ass grow in the making or you dont know what ' and '' means hopefully u got a big grow otw and your gonna get us some pictures