Kaezziel, I've got an Invader Mini and there are some great deals on the VT as well. Saw it, the VT, for 64 bucks today. I tried Ni200 and got a metallic taste so I'm using titanium now. I will say it's easier to get a higher resistance setup with Ti versus Ni but Ni has the advantage if you're a sub-ohmer.
Switching to Ti only took a little fooling with temperature on the Invader. I'm running a Fogger V6, with modified air flow, at a net of .36 ohms, 23 watts and indicated 280F for temperature.
I find the Invader does not necessarily display temperature accurately. I was able to boil water at 200F with both Ti and Ni which should not be possible with either. The auto shutdown feature can be a pain and, sometimes, it forgets what it was set to when it wakes up. That seems to be a "feature" of the V1 or early release ones. It's more of a pain than a serious problem to me, the first drag can be a little "weak", it comes up at 10 watts, LOL.
It is one tough device. I use it outside while working in the yard and just rinse it off under the tap when I come in to get the dirt off. I don't know o any other mod that you can do that with.