You can shop forever, and try many different cartomizers and atomizers. They are not all the same, there is quite a bit of difference. On a VV, you can make almost all of them work the way you like by changing the voltage. Different mixes of E-liquid vape differently depending how many volts you slam into them also. Some juices like lower voltage in the same atomizer and higher in others. The idea behind VV is to put you in controll, instead of your battery calling the shots or one particular brand of cartomizer/atomizer. It's horrible to be locked into one product, and hope they are not out of stock, or charging you too much. Wonderful to have options, and shop different vendors, and try different products.
It's all about freedom to vape how you want, and custom tailor your vaping experience.