First of all, the four variants are as follows: Droid DNA (on Verizon), J Butterfly HTL21 (on KDDI's au network in Japan), Butterfly X920d (for Taiwan, South East Asia and India) and Butterfly X920e (for China and Russia). It goes without saying that these devices carry different radios to cater to regional needs, with the Droid DNA and the J Butterfly both supporting CDMA and LTE on top of UMTS. However, only the Droid DNA comes with quad band UMTS radio, thus making it a better global phone. On the other hand, the X920d and X920e serve mostly in areas without LTE (except for Singapore), so they naturally lack this 4G technology.
As expected, there are subtle differences when it comes to color accents and logo placement. Most notably, the X920e for China and Russia is the only model that comes with red capacitive buttons instead of white, and for some reason the J Butterfly managed to get away with no logo placement at all on the front. While on this topic, the Droid DNA is given the Verizon logo near the earpiece, and it also gets a matte black finish.
The only obvious physical difference between the two main body designs here can be spotted at the top right corner. On the J Butterfly and the X920d you'll find a flap over a compartment for both the microSD slot and SIM tray, whereas the Droid DNA and the X920e -- both 2mm shorter than the other two -- have just a common pin-eject SIM tray at the same spot. The J Butterfly stands out further by packing an infrared port next to the rear camera, as well as three metallic contact points for docking towards the bottom of the back side.
Internally, the Droid DNA is again a winner with its exclusive Qi wireless charging feature, but this does require some extra space, making the model 0.65mm thicker than the 9.08mm-thick X920d and X920e. That said, apart from the X920d the remaining three models all come with NFC.
So overall, we'd say the Droid DNA is almost the perfect model out of the four variants: it has pretty much all the radios one would need, and it does wireless charging. Slap a microSD slot and extra LTE bands on it and it'd be the phone of the year. Well, at least until MWC, anyway.
Update: HTC has provided the correct radio bands for the J Butterfly, and we've added them to the table below.
Myriam Joire contributed to this report.