This is my experience with the 3 listed and is for all the newbies that wanna change tanks 
Lets start with the vivi nova since i have most experience with those... They are ok, not alot of flavor and the rubber head on the coil tend to be a little to long and might need a little trim, after that theyre good but at times a little growly and might have a burned/plastic taste...
BUT they can produce a good ammount of vapor and can be taken apart with ease for cleaning and so on
(If you must have one take the v3.0 thats the one i find the best personally)
Kanger protank
Produces a perverse ammount of vape, has decent flavor and is overall very nice, no burned or plastic like taste at all
BUT the draw is really airy and does seem a little wierd
Core 65 v2.0
ALOT like the vivi nova but not growly or bad tasting, a little wierd to take appart but the double chamber system works great, theres not a hint of growling what so ever and produces a good cloud
BUT not as tasty as the kanger protank i must admit, its more like the vivi novas
The prices are about the same but the kanger is the way to go if you can handle the airy draw but if you dont like sucking through an empty straw go with the core 65 v2.0
All vaping was done using a lavatube vamo at 4-4.7 volt with 1.8-2.2 ohm
Testing both taste and cloud
Lets start with the vivi nova since i have most experience with those... They are ok, not alot of flavor and the rubber head on the coil tend to be a little to long and might need a little trim, after that theyre good but at times a little growly and might have a burned/plastic taste...
BUT they can produce a good ammount of vapor and can be taken apart with ease for cleaning and so on
(If you must have one take the v3.0 thats the one i find the best personally)
Kanger protank
Produces a perverse ammount of vape, has decent flavor and is overall very nice, no burned or plastic like taste at all
BUT the draw is really airy and does seem a little wierd
Core 65 v2.0
ALOT like the vivi nova but not growly or bad tasting, a little wierd to take appart but the double chamber system works great, theres not a hint of growling what so ever and produces a good cloud
BUT not as tasty as the kanger protank i must admit, its more like the vivi novas
The prices are about the same but the kanger is the way to go if you can handle the airy draw but if you dont like sucking through an empty straw go with the core 65 v2.0
All vaping was done using a lavatube vamo at 4-4.7 volt with 1.8-2.2 ohm
Testing both taste and cloud