Well, I'm not exactly the person you were looking for to reply, as I haven't used an iStick, but I was just in the same situation as you. I have an MVP v2. I dropped it and the 510/ego connection is now loose. It still works, but is a bit wobbly now. I was going to replace it, but after reading all of the raves about the iStick, I thought I'd give it a try. After all, it is roughly the same price and provides more power. The MVP at 11 watts is sufficient with most of my builds in my Kayfun, and more than enough for my Mini Pro Tank 2, but occasionally I find myself wanting a bit more power for certain builds in my Kayfun. From what I read, the MVP is a little more durable though, and has better battery life.
Well, the MVP v3 is rumored to come out around Christmas, so I thought about waiting for that...but I'm impatient so I went on the search for an iStick. Sold out (at least in the color I wanted) everywhere I looked. I didn't want to spend a fortune, so the decision became "wait for the MVP v3, or wait for the iStick to come back into stock. What decision did I make?
I bought the VaporShark rDNA 40. $225 for the device, sharkskin, and wireless charger.
The moral of this story is:
Never go mod-shopping after drinking too much Jack Daniels.
I can't say I regret my decision....in fact, I'm really excited, but without Jack speaking in my ear, I'd say if you have to get it now, get the iStick. If you can wait a month and a half or so, wait for the MVP v3.