They're the same, more or less. The parts are compatible. The VK, according to some who have used both, is a little better. The VK gets changes to improve performance. Steve's always trying to make the product better. There's a longer battery available. 10 second cutoff time is coming on future manuals, vs. the current 5 sec. No cutoff on the manual Pass
through. Cart flavors are very good too.
As for sticking buttons, haven't heard of any problems with the VK but I'm pretty new to e-cigs. The VK warranty is open ended and you don't even have to send a bad battery back for replacement, just let 'em know you have a problem. They'll send a replacement with your next cart order. With a 10% off code available, and something extra in every order, the VK is the way to go IMO. I got a free PCC with my first order.