I have an IQ2. It's very portable and very robust, and you can dial in the right temperature. However it takes ages to heat up in comparison to other devices I have. A couple of minutes I think, though I haven't timed it.
I reach for my legacy pro more often, because it performs slightly better and is much much faster (takes 10 - 15s to get up to temp). If you get the dosing capsules, it becomes even easier to use (without them it can become a bit messy tbh). This is portable, but slightly less portable than the others IMO because the mouthpiece has a tendency to come off. It's only a little thing, but it could quickly become annoying in a handbag or whatever.
My OH uses a Pax and I can see why she prefers it. It is far simpler than the others, and looks much neater. It doesn't have a removeable battery, but it has a decent battery life (3000mAh, about the same as one with a removable battery) and it's quick to charge. The performance is not as good as the legacy pro, but it's not much longer (20s ish to get up to temp) and it is so much better for carrying about, that's the one I take if I'm off out to a gig or something.