Well, you all have covered this topic very well and I really can't add much, but I'm sitting here at 2:30 in the morning, wide awake with nothing to do.....so I'll add my two cents. lol
I switched to the Volt from the eGo about a year ago. Loved the slim bats and cartos! But I had to try the x2 when it came out and was surprised to find I like them too, and use them with both clearos and cartos.
To be satisfied with vaping I have to have a variety of flavors to switch between. So my usual setup each day is one or two x2s and about four regular Volts. When I leave the house (I'm retired) I just take a few slim bats with me. If I'll be gone a while I take the case and/or pcc along with spare cartos.
I also have two 3.7v wood box mods, which are beautiful and fun to use. But being a girl-type I only use them at home. lol So I like some variety in hardware and a lot of variety in juices. But my very favorite setup is still a 65mm auto Volt with a regular carto and a drip tip. But I'm not set in my ways and I'm working my way into more 78mm bats.
I failed my first attempt at vaping. Just lasted three months using the Joye 510. But I started again last year on May 1st. I credit SI with being able to keep with it this time. Their hardware just does it for me. And they stand behind that hardware with great customer service.
So to sum it up: if it works for you, that's what you should use.