Hi, I'm very new to the flash kits stuff. After looking through forums and web sites, I'm getting more confused. What's the difference between the Slot-1(R4DS) and the Slot-2(G6Lite and EZ-Flash IV Lite)? The Slot-2 flash kits, in particular, the G6Lite and the EZ-Flash, comes with a USB adapter as well. Appreciate any answers. Thanks!