I don't have the VP1, but I do have the Xtar SP1. I absolutely love that thing!!!
It's only a single bay charger.
Performance wise:
-It charges my 18500 batteries super fast because you can charge AW batteries at 2 amps.
-It can charge batteries from --350 up to 26650 with no hassle, manipulation, or spacers need.
-It can charge IFR (LiFePO4), IMR (LiMn), and ICR (LiCoO2) battery Via the manual voltage switch (i.e. if you are charging 3.7 volt AW IMR set it at the 3.6V setting).
-It has a very good charging curve (very similar to the VP1 as well)
-It can charge batteries faster because of the 2 amp setting (if the batteries can take it like AWs can)
-It has the soft start for over discharged batteries
-It cuts off right at 4.2 volts EVERY TIME (for 3.7 volt batteries).
-Comes with the car adapter too
Honestly the SP1 is every bit as good as the VP1 from what I have read. It's been an awesome charger for me but I don't need a 2 bay charger. It is only 20$ +/- 2$ so you could get 2 for the price of one VP1 and be able to charge at 2 Amps and fit up to 26650 batteries.
I love it and reccomend it to anyone who asks for a really good battery charger. Don't let the price fool you, it is awesome! (you do only get 1 bay remember)
Here is a link to someone that knows more about chargers than I do.