The only big differences are the 300 amp continuous rating (1500 intemittent), and the fact that the second battery is not switched into the system untill the first one's voltage comes up. The NL kit keeps them separate after starting for a fixed amount of time, then joins them.
I didnt hook up the cab controls since I didn't care about being able to join them manually from inside the cab. The VSR has a manual switch on the box itself that switches it from off, to auto, to on. the switch forces it to be in any of those conditions no matter what the charge voltage is. I figured that the only time i'll need to mess with it is if the main battery goes flat, then its easy enough to pop the hood and flip the switch.
I didn't do the NL kit because I knew i'd want to upgrade cables, I liked the way the VSR worked a little bit more, and the VSR can handle general winching loads (didn't have to worry about it being on while winching). If you take the cables out of the equation the price of the VSR (I found it for $150) versus the NL solenoid ($140 from equipt) is not too far off, and the battery monitor would be used in either setup.
The cables are what really cost money...