Like everything else, there is no one answer for everyone as to what is "best". It all depends on what you do on vacation.
For me the iPad would not do as a laptop replacement. I like to take a lot of pictures, usually in RAW format when I'm on vacation, then color correct and edit them. The iPad doesnt have enough space, and not enough power for RAW to jpg processing. Its great in the car for listening to music, playing on the internet and maps though.