I am not brand loyal or Vendor loyal. The Vivi Nova FT sells are knockoffs are are sometimes problematic. I've been using Vision brand Vivi Nova 3.5 ml for 11 months. My heads ate lasting 10+ weeks and are cheap and easy to change. My operating cost for my Vivi is 14 cents per week. The ProTank I've never tried as I'm very happy with my Vivis. Most of these clearo/ tank setups have the option to replace the head thus making it easy and cheap. Realize if vaping "acidic" juices the plastic will degrade. The ProTank is glass so there's no problem.
Here's a good price for the ProTank- use the discount code:
Vapor Joes - Daily Vaping Deals: LOW: Kanger Pro Tank - $14.05
Just a note... you can also get a metal tube for the Vision Vivi Nova at around $3-$5 a pop depending on where you buy it from. These will also prevent acidic juices (citrus, cinnamon, sours, etc.) from cracking your tank. And to me, they're more attractive than the clear tubes, which is an added bonus.