My first vv device was a twist and it's a great device. Do keep in mind that like any Kgo/Ego style battery the battery is the device. How long it will last I can't be sure, but if used heavily you figure 6 to 9 months. For the price, it can't be beat. If you're really looking for a long term VV solution, you might consider starting out with a Lavatube or similar device ($60 and up). You can buy batteries for it that will last you a day (depending on how much you vape) and the battery can be replaced and bought at most any online vape shop for $8 to $12 (depending on brand and mah rating). But the device should hold up for a long time. Some of the Lavatubes and other such devices will also tell you the resistance (ohms) of the tank or atty you've attached to it. Part of the advantage of a VV device is being able to adjust your voltage by the resistance of your device and having a PV that can tell you your resistance makes that easier. The twist is just a battery so it doesn't have that capability. Still, you might do fine adjusting by "feel" (eg. Twist until the vapor, flavor and throat hit are where you want them). Your budget will be the determining factor at the end of the day. all told, should you decide to upgrade to a fancier VV, the twist makes for an excellent backup device. You can't really go wrong.
Novas for me are hit or miss (mostly hits and it could be due to the version I have which is older than the 2.5s available now). Easy to fill, easy to clean, looks nice, you can use your own drip tip and replaceable coil heads are pretty cheap. But, like any wick style clearo, you may get muted flavor, the occasional dry hit and you will quickly learn that this thing prefers to be on its side to wick juice properly, especially after your at half capacity in the tank. Not a knock on the Vivi as this is true of most, if not all, clearos, but important to note. Again, for the price, not much to lose and if you like it all the better. If you do buy a twist be sure to pick up a metal twist on "skirt" that you will screw on to the twist first, followed by the Nova. This gives it a sleeker look and helps stabilize the nova (which is much wider than the twist) so that you don't accidentally snap it off the battery if it gets caught with something. I wish I had a link to one handy so that you can see what it is, but you'll find it nearly on every shop under the accessories category where adapters and such are listed. And finally, get the 1000 mah battery. Yes, it's as long as a lavatube or Provari with the extended cap, but the extra battery life is worth it.
Whew! Sorry for the long reply and hope this helps!