I have both the Prodigy and the Xhaler, so I can offer my take:
The short answer is this: I like both units for different reasons, but I prefer the Xhaler.
The Prodigy:
Pros:
- Button placement
- Runs under load at almost exactly 5 volts
- Adapter reservoir for catching any leaking juice
Cons:
- High switch failure rate (with the electrical switch) - I've been through 3 switches in about 3 months
- The lower threads on the tube tend to strip and crossthread
- Performance drops off quickly when the threads or contact points get dirty
Xhaler:
Pros:
- Adjustable voltage
- Mechanical switch
- Runs at about 5.6 volts with the resistor engaged
- Seems to run consistently without constant cleaning
- Built like a tank
Cons:
- the 801 adapter doesn't work with my BE112 attys, so I have to use a 901 -> 801 adapter on the 901 tip - with a staple mod - to make them work.
- The button placement takes a little getting used to. That being said, I've grown to like it now.
In Use:
The Prodigy is my 'go to' device for running 510 attys at 5 volts. Since the Prodigy runs at almost exactly 5 volts with the resistor, it's the perfect machine for feeding my 510's. The Xhaler with the resistor engaged runs a bit higher, at about 5.6 volts. This is too harsh with my 510 attys, and tends to burn the juice.
On the other hand, the Xhaler is absolutely perfect for running my BE112 (801) atomizers with an Altsmoke adapter on the 901 tip. It hits about 5.6 volts with the resistor engaged, which powers the 801 beautifully. Also, once the batteries start to fade a bit I just unscrew the bottom cap and I'm good to go for another few hours. It's an excellent design, and it works flawlessly for me.
In short, both are great devices, but if I had to choose one, I'd have to choose the Xhaler. The Prodigy is certainly a great device for running 510's, but it is handicapped by its frequently-failing components. It just hasn't been reliable for me, which is important for what should be obvious reasons.
Finally, the Prodigy looks a little bit sexier as well IMO. Of course, I'll trade this any day for a device I can rely on like the Xhaler. ;-)
Hope this helps,
...D