Both the Kr8-compatible VOLT and the 510-compatible eGo are excellent PVs. [The term is PV, not VP.;-)] Either can produce great vapor, flavor, and TH ... with the appropriate atty or carto. And you can use blank or prefilled cartomizers on either (except there are very few prefilled cartomizers for the 510). [Unless you don't mine the frequent effort of direct dripping, I do recommend cartomizers over atomizers.]
The main differences between them are the obvious ones: size/shape, manual vs. automatic batteries, and mAh. If you prefer one over the other because of those differences, then just find the cartomizers for that model and
e-liquid that are most satisfying for you.
You seem to like the VOLT cartos. Be aware that they can be refilled with the e-liquid of your choice and that blank VOLT cartos are available for filling from scratch. IMO the best Kr8 cartos (with one exception I will describe) are the VOLT (and the more expensive virtually identical Bloog Maxx Fusion and Halo G6). But many vapers love Vapor4Life's Wow and Premium cartomizers ... or others, which I have not tried. The one exception is my current favorite: CigEasy's Elite 808. The 2ml-capacity cartomizers are longer and somewhat wider than the VOLT's, but they are fully compatible and work just fine on VOLT batteries, just not as streamlined a look. You might want to check them out at some point.
My favorite 510-compatible cartomizer for the 3.2V eGo is the Smok Tech 1.7 ohm Mega
Single Coil, e.g., "The Resurrector" from Crystal Clear Vaping. Outstanding vapor and, especially, TH. [The dual coils don't hit hard enough for me on 3.2V.] Speaking of 3.2V, TH, and that Elite 808: The Elite cartos have very strong TH on the Elite 3.7V battery ... sometimes too strong for me. So I often use them (with an inexpensive 510-to-808/901 adapter, e.g., from Good Prophets) on my eGo batteries. The eGo cone doesn't fit over those slightly wider cartomizers, but it is a wonderful vaping experience.
Once you get the battery/cartomizer combinations worked out to your satisfaction, you can begin the most most important part of your exploration of vaping:
e-liquid. And there are so many flavors and suppliers to choose from. It will take you awhile. I've been at it for over two years and have barely scratched the surface of what is available.
Enjoy the adventure!