I prefer the Apple Wireless keyboard for travel. It is ultralight, is reliable and fits in my travel pouch perfectly. Usually stand up iPad and use keyboard in my lap.
I've used the Apple wireless keyboard as well as Logitech. At the moment, I prefer Apple because it's more comfortable to write with, although Logitech is better for portability. I've written more in detail about what I think about both here:
I'd go with the Logitech K760, because A) you can connect it to 3 devices and switch between them, B) it's lightweight so you can carry it around, C) it works with the Mac, too and D) it charges itself by frickin' light via the solar cell: