I made the same decision when I bought mine from SAM's. Just too steep a price for the minimal increase in battery capacity in my opinion.
As far as the L16's, they are too tall to fit just about any place and it's putting all your eggs in one basket; if one fails, you are screwed. 4 GC-style batteries are not going to leave you without power if one of them decides to act up. And for the price of L16's, it's getting real close to LiFePo batteries that can be drained down to 20% and weigh half as much as flooded. (Besides zero maintenance and able to be mounted in any direction.)