I would def get a kGo or an E-Power over an eGo. The eGo is only 3.3-3.4V, while the kGo/E-Power are both 3.7V PVs. The 3.7V PVs provide alittle more "oomph"(slightly warmer vape and alittle more TH) and more importantly, they handle the lower resistance attys/cartos a lot better.
With an eGo, I dont recommend using anything below 2.0ohm. Many people do use cartos below 2.0ohm on an eGo, but a lot of people have also fried an eGo bc of it. Using 1.5ohm or 1.7ohm cartos puts a lot of stress on the eGo mosfet and if your not careful, they can fry the mosfet, which turns your eGo into a paperweight.
The kGo and E-Power can handle the 1.5ohm and 1.7ohm cartos a lot better, and can even handle the 1.25ohm cartos, although I dont recommend using them bc they void the PV warranty.
Personally I like the E-Power the most bc its the only one out of the PVs mentioned that uses non-proprietary batteries, which are removable. E-Power batteries cost $4-5 compared to eGo/kGo/Riva batteries that cost $14-20, and the E-Power batts last longer before they need to be replaced. Also everything on the E-Power is replaceable so its cheaper to maintain. I also like that its very easy to carry a spare battery for the E-Power. The batteries are about the size of a AA, but alittle longer so its easy to carry an extra in your pocket/bag and if needed unscrew the switch and pop in a fresh battery. With the proprietary battery PVs, like the eGo, kGo, Riva, to carry a spare battery you have no choice but to carry a second PV. The E-Power batteries are 1050mah and I get on avg a day to a day and a half on one battery.
Honestly I think youd be really happy with a kGo or an E-Power. Their both great PVs that are affordable and give a very nice vape. Both have very good battery life (kGo-1100mah / E-Power-1050mah) so you wont need to change batteries constantly.
Hoosier has a good deal on the kGo, and Crystal Clear Vaping has a good deal on the E-Power. Hoosier also sells the E-Power, but they are sold out right now.
The deal at CCV is another reason I picked the E-Power over the kGo. You get about $25 in free stuff from CCV which makes it a really good deal. The price is alittle more than what other vendors charge, but once you add in all the free stuff you get, it makes it an awesome deal. You get a free 5-pack of Ressurector cartos, a free 30ml juice of your choice, and free shipping. Also put in "ecf5off" to get 5% off the order.
If you do get a kGo or E-power, I highly recommend trying the Ressurector cartos. They are designed for 3.7V PVs like the kGo/E-Power, and they work awesome on both devices. They are 1.7ohm so they give a nice warm vape and they hold about 2ml of juice so they last a pretty long time before needing a refill. The Boge 2.0ohm cartos are also good cartos, but I prefer the Ressurectors bc they hold about twice as much juice. The "Ressurectors" are really just a nickname, and they are really the Smoktech 1.7ohm XL cartos. CCV is the vendor that gave them the "Ressurector" nickname, and they call them by that. Hoosier calls them the Smoktech 1.7ohm XL cartos, but regardless of the name, they are the same cartos.
They will also work on an eGo,but they dont run at full potential bc the eGo is only 3.3-3.4V, instead of 3.7V.
And if you want to be able to go even longer between refills I recommend getting a Smoktech 3.5ml tank. The Smoktech tanks work really well and are super cheap. You can get a 3.5ml tank for about $10, and it comes with a pre-punched carto and drip tip, which makes it an even better deal. Smoktech also makes a bigger 6ml tank, but personally I prefer the 3.5ml tank. I think the bigger tanks just look kinda funny on an E-Power/kGo sized PV and they make the PV top-heavy. Their great on a bigger mod, but on a smaller E-Power/kGo/eGo/Riva, their just kind of awkward bc the tank is considerably bigger/fatter than the PV. The 3.5ml tank is about the same diameter as the battery tube so it looks nice and doesnt make the PV top-heavy. The Smoktech tanks are dual coil tanks, but that doesnt mean you have to use DC cartos. Personally I think dual coils suck at lower voltages so I didnt even use the DC carto that comes with the tank. Instead I use the Ressurector cartos in the tank and they work a LOT better. They are single coil, but they are the same size as a dual coil carto so they fit perfectly in the tank and work great.
CCV and Hoosier both sell the tanks and also sell pre-punched Ressurectors for the Smoktech tanks that have the metal base on them, like the DC carto that comes with the tank has. You dont necessarily have to use a carto with a metal base on it, but they are nice bc it stops the tank from being able to slide down and also keeps the carto in place when you pull the drip tip off.
Heres what the 3.5ml tank looks like:

The first picture is of a 3.5ml tank with a Ressurector in it, and the second picture is of a Ressurector by itself.
As you can see, the 3.5ml tank doesnt make the PV alot bigger or bulkier. While it is the smaller tank, it still last a long time before needing a refill. I really like the 3.5ml tanks bc they are big enough that I can go all day without needing to refill, yet their still small enough that I can easily carry my E-Power in my pocket with the tank on it.
I would def consider getting something like this if you get a kGo or E-Power. I think a Smoktech 3.5ml tank with the Ressurector cartos is a perfect set-up for anyone that has an E-Power, kGo, or Riva.
With the long battery life of a kGo/E-Power and a 3.5ml tank, you can have an all day maintanence free vape, while still having a very portable PV.
I pop a fully charged battery into my E-Power in the morning, and also fill my 2 3.5ml tanks with my 2 favorite juices before I go to work, and I can easily vape all day completely maintanence free, and dont have to worry about needing to recharge batteries or refill cartos. Its a very affordable set-up that is simple to use, requires very little maintanence, and gives a great vape all day long.
Goodluck with it!!