For those vapers who use off-the-shelf devices, variable voltage/wattage is the way to go. It used to be said around here "once you go VV, you'll never go back". It allows you to turn the power up and down, fine-tuning your vape to give you the experience you desire. You can most certainly do this by changing from standard to low resistance and vice versa, but changing the device is more cumbersome. All of a sudden you have multiple atomizers/cartomizers/clearomizers with varying resistances, but you only prefer a few of them. Rather wasteful of time & money; simply adjusting the battery power is much easier.
Another advantage of a variable voltage/wattage device is that they will keep the power level constant throughout the life of the battery. From the first hit to the last, each one should be the same. On the other hand, if you want to increase or decrease power throughout the day, depending on your needs, you are able to do just that. The juice you want to use doesn't like that much power?....no problem. Just turn it down a little.
For a decent vape with standard ego batteries, try the T3/Evod/Protank devices. The bottom coils work very well with the standard ego batteries, giving good vapor and flavor without all the heat.