I've worked for the airlines for over 30 years and my experience tells me that when you start and check in a bag that looks like it has expensive equipment in it, it has a higher chance of going missing and never turning up. I am not saying that all airline employees are thieves but in large airports you have all sorts of other people that have acess to the baggage makeup areas.
I was faced with this dilema when I got my 500 f4 and the 300 f2.8. I researched a number of different cases and even looked into having one made. I ended up buying a simple hardsided Samsonite suitcase. In this I put the 500 which I have in a Lowepro softsided case, the 300, a variety of accessories and some clothes just to make sure that it is firmly enoug packed so that things don't move around. It has a key lock as well as a combination lock. This has made alot of trips and I have never had any trouble with it and it has always arrived with me. These suitcases are quite often as expensive as some of the pelican cases. One could always buy foam padding to put in there if they felt it didn't offer adequate protection.
Since doing this I have found a few other photographers that do the same thing and have had the same success rate that I have had.
One thing to note, airlines have a maximum liability on checked baggage so check with your homeowners insurance policy to see if this is covered while travelling (mine is). You can also declare additional value at the airport and pay an additional charge for this. The insurance is just peace of mind in case something does go wrong.
The airlines are getting real sticky about the amount of carryon baggage so don't try and take anything that is oversized. I hate to see people trying to board their aircraft and then are forced to check the item at the gate and it ends up in the baggage hold anyway.