From what I remember, on the Sound Devices you can set it to start at whatever number you want.
I've never used the PD6, but I have used a SD722 a lot and I loved it. It's super portable, veyrvery lightweight and really easy to use. If you're announcing your takes at the beginning of recordings the track/take number it displays is the one you previously recorded. The built in Pre-Amps in the Sound Devices are great.