I go back and forth with this every trip! I've used both Pelican cases and backpacks and each has their pros and cons.
If I check my camera gear it goes into a Pelican case. That's my least favorite option because 1) the case itself draws attention and 2) if it does go missing, everything is gone. So I prefer to carry it on, at least the basic rig and my laptop. I have a couple of backpacks, my favorite is the Lowepro Mini Trekker because it's compact yet holds alot. I also have one that will hold my laptop but it's bulkier, heavier and less comfortable so I carry my laptop seperately. Luckily the Oly PT cases are small so I can get all my camers gear in one backpack. Another good point to a backpack is when I wear it up to the check in counter, I've never been asked to weigh it! YMMV
There's a new Pelican case, model 1510, that has wheels and is carry on size, 20x14x9.
Cases4Less.com has the best price I've found. The only problem with carrying on a hard case, even if it fits the required size, is it's hard to fit in the overhead compartments.
Whatever you decide...have a great trip...and bring back some photos to share!