I like the ZMF-II.. It retains the last three time controls used. Is easy to see the LED when in a long game and you get up from the board. Only drawback is if you play lots of speed chess. There is no flag ICON, so the numbers flash, which makes it very easy to see. The NA DGT has the flag icon. Before you buy one, if you intend on tournaments, go to USChess store and verify the one you plan to buy is a tournament possible clock
For those wanting a very good clock without spending a lot of money, I recommend the Xflyee clock you can get on Amazon. I wrote a detailed review of the clock in this thread: https://www.chess.com/forum/view/chess-equipment/xflyee-chess-clock. If you want the best clock and don't mind paying more for it, get the VTEK 300.
If you get a ZMF-II (or other Z-Mart clock), make sure you get it from the manufacturer directly. I think this is the only way to ensure you get a clock with the latest firmware that has fixed all the major bugs and other issues that are present in earlier firmware editions of the clock.
I like playing with the DGT NA. The only thing that bothers me is the same thing previously mentioned about DGT clocks - the fact that resetting it involves picking it up and turning it off and on. It's a fairly mild complaint, I admit, but it still irks me.