Here's my thoughts, from two different angles.
It's pretty hard to beat the Vivi Nova Mini (with the neptune metal tank especially) once you have rewicked it. You can go two ways: flammable (cotton, bamboo thread) and non-flammable wicks (silica, ceramic). Better wicking and flavor production will result with flammable wicking material (and cotton is cheaper than silica or ceramic wick) than non-flammable (which is the main gripe about Vivi Nova Minis). If you want to take a chance with silica wick (there have been threads warning of micro particles being released by it) then that's all you. Just remember you will have to rewick it all the time if you use a flammable wick which means you'll go through more nichrome wire. I'd say the cost balances out but the maintenance time is increased. Plus it helps if you have an APV with an ohms readout or you'd better get your math up to par with measuring the length of the wire you are using (and coil diameter vs resistance chart over length).
If you go with the replacement heads they sell you will have to dry burn it every few days. The coil will get coated and have a burnt taste. Just wash it out, blow through the airhole (battery side), dry the wicks with a paper towel (squeeze, don't rub - the wick/coil is fragile, if you pull you can either ruin it or push the coils together and make hotspots which ruin the coil's performance AND durability), run the hairdryer on it and then dry burn it. Once the coil glows red stop hitting the button and BLOW REAL HARD on it. This will keep the fire going on the crud but not the coil. Do not blow on the coil with the button on or it will melt the coil. Keep doing this in quick bursts (to light the crud and then keep it going with airflow) and blowing the ash off and the coil will clean itself with little damage to it. You can keep a silica head going for literally months if you do this. The traditional practice is to cook the coil in few second bursts until it's clean but I find that the wick WILL melt in half if you do that and ruin the head.
One thing you'll want to do either way is get yourself a chrome or glass drip tip. The plastic ones it comes with are huge and they basically suck. I prefer chrome for its durability/streamlined looks (matches the top). You drop your Twist and Nova with a glass drip tip and you may have a bad day. Most people don't carry around spare drip tips either.