Just my 2 cents to consider also. I have a 12ml bubble type cover that is heavy. I couldnt imagine having a 16ml or anything higher than 12 due to the weight. Heavy covers will indeed last longer but you better have a comercial type solor cover reel, or cut it in very managable sections to remove and put back on if your getting one larger than 12ml.
I have an irregular shaped pool so a managable cover is more important for me, a standard shape will be easier to manage with a heavier cover. Just something to consider.
My last cover was a 12ml clear bubble and it did warm the water better than the previouse blue cover I had. It was the best combination of heat transfer, retainment and durability of any bubble type I had.