1. Appearance...I like the d4 much better. And it has a much larger and brighter screen.
2. No LiFeO4 support on the Efest.
3. No support for NiMH or NiCad with the Efest.
4. In HKJ's review, his charger consistently overcharged, even to the point of tripping protection in some cases. This was true on all slots. That is not only going to increase wear on the cells, but is potentially unsafe. Edit: I read the updated review, and apparently they fixed this problem.
5. In HKJ's review, he found the voltage read .06V too low on the Efest.
6. HKJ feels that 500ma is too high for 10440, except for IMR. If you pair two 10440s in the d4, 375ma is less hard on the cells.
If you get the updated version, the Efest seems good for li-ion (except 10440). But it isn't a universal charger like the d4, which can handle NiMH, LiFeO4, and NiCads in addition to the standard 4.2V li-ion.
To each his own, I say. But I'm very happy I went with the d4.