Mint 14 as a second choice. Kubuntu does a regular install onto a flash drive which becomes 'persistent', allowing changes in the program, add new programs, save files to Home folders, and boot from it, which is like having all a Live DVD install capabilities of booting almost any computer rather than tailored just to the one the install is done with. It's the best of both worlds.
Mint Live DVD is easily installed to a first and single partition on a flashdrive in FAT32 file system, but only windows can see the rest of the drive to save files to. You can however gparted the drive, shrinking the first partition and creating a second partition which Mint can then see to use as storage area. That second partition's folders and files won't be seen in windows, so gives some limited privacy from other windows users accessing it, unless they realize the flashdrive is bootable into Linux.
I found Kubuntu easier to work with, easily given a more windows friendly look, starting from the Start Menu appearance. Mint on a full install removes some programs and driver files, thereby limiting it's usage mainly to the computer it's installed on. That's fine for a hard drive install, not so great if you wanted it on flashdrive to boot other computers.
For hard drive install, so long as you know how to install programs Mint 14 drops like gparted, then both are good. For Flashdrive installs which can be booted from a variety of computers, Kubuntu works best.
Here is how my Mint 14 flashdrive is setup. After this screen capture I shrunk that boot partition to 100 MiB and added the extra onto the next partion used for system install.
Here is how the Kubuntu 12.10 on flashdrive install appears.
Here's my Kubuntu desktop with adjusted menu, font and sizes adjusted to personal preference, a background photo, added Thunderbird and Firefox programs. I have 4 different desktops setup on it, each with their own background and specific programs to use.
Just my opinion, but I feel Kubuntu is most windows user friendly. I think the Mint MATE desktop version is a bit behind Kubuntu, but it's a great distro nevertheless.