I need to secure some work on my laptop and an encrypted disk image fits the bill. I don't need to hide the file (diskimage) just the contents. I like a sparse disk image since it will expand as I add content but a Truecrypt volume "feels" more secure to me. Is it really? I'm not hiding it from the NSA, just someone that might steal my laptop or access it, etc.
Is there really much difference?
I would guess that the weakest link isn't the choice of formats, but your picking a decent password and not letting it get observed or captured.
In the general case where there is a system tool and a third party one, I usually start with the tool that is built in until I have good, definite and enumerable reasons to not use the default tool.
Go with encrypted disk images in the case you have set out.
