Depends on how you plan to use it, and how much footage you plan to take. Format of the data will be the same on both disk and card.
A hard drive recorder will usually have a greater capacity, but with memory card prices dropping rapidly you can also get quite a lot of video onto easily available 4GB/8GB/16GB cards.
Hard drives camcorders will need to be treated more gently than card based recorders because of all the moving parts - so if you are going on an extreme action holiday perhaps Card would be best.
How do you plan to store the material. If you want to keep it all on camera until you return, then hard disk has more capacity, but if disk crashes at any time then you will lose the lot. Are you taking a laptop to transfer material onto DVD as you go?
You could use multiple memory cards, so if one goes wrong you don't lose the lot. Could also send them by post to someone else to archive for you.