The 1500 is much smaller than the 1510, and the 1510 has wheels. The 1500 is a great case (all Pelican cases are great!), but over time, those wheels are going to make your life a lot easier if you do much transporting.
I do think they are much sturdier than a birdcage, but I think well-built birdcages are pretty sturdy and a good solution for a lot of people. They just don't let you carry all the extras. The birdcages are great for showing off the chips, but that meant nothing to me personally. My biggest objection to the birdcages wasn't the case itself, it was the fact that I like the 4x25 boxes better than the 5x20 racks. Since the birdcage is lighter than a Pelican, if all you need is 1000 chips (or 600), a dealer button, and up to 4 decks of cards, they would work quite well. Once you need to carry more equipment, it doesn't work as well. Those are some of the reasons I prefer the Pelican.
TFCJ, I seriously considered the 1560 too! I really liked it, but went with the 1520 for two reasons. One is that it will qualify as on-board luggage and the other is that it was big enough to cart 1500-1600 if I needed to. But the 1560 would hold a lot more -- a whole lot more. I may still get one, though I'm concerned about the weight when fully loaded. I have a 1600 and a 1700 chip sets, and I'd love one case to carry them all. My biggest issue is how much it all weighs. I'd love to know how you like this case as I still consider it a viable option for me. I was thinking of getting another 1510, or getting going ahead and getting a 1560. I'd get the lid organizer. I love the lid organizer in the 1510, and the 1560 LO will hold even more.