The VTF3 mk4 is much like the mk3 with some improvements, the most notable of which is the addition of the Q control. Supposedly the driver had a few minor improvements as well, which slightly reduced distortion and improved headroom a bit more in the upper bass. So you see, the mk4 is very comparable to the mk3 regarding overall output ability.
Now compare the Outlaw to the Hsu, either mk4 or mk3. Same bash amplifier power, same cabinet shape and volume, similar driver. The key difference is the ports, the Hsu have wider and much longer ports. As you know, this is a big advantage in low frequencies for cleaner and stronger output. Simply put, the VTF3 is a lot like the LFM-1 EX, except better deep bass, a couple more configuration features for the mk4, and some other small improvements. Hsu had a hand in designing the Outlaw subs, I don't know if Outlaw modified Hsu's designs at all, but the Outlaw is really just a slight modification of the VTF3 mk2, the only difference between those two subs is the ports are on the rear of the mk2 as opposed to the underside of the LFM, which, of course, is going to do very little to differentiate performance between the two.
BTW, I don't see where you find superior measurements for the Outlaw on the Hsu. I don't think Ilkka's numbers can be compared to Ricci's, if that is what you are doing. After all, compare Paul Apollonio's measurements of the FV15HP to Josh Ricci's, same exact unit and they had some very different numbers. Both are guys who knew what they were doing, so from that I take these data sets should only be used to compare subs from within themselves. Hell, compare Sound & Visions measurements against Audioholics for the same subs! So much for CEA2010...