I fail to see how "Von nebula" is unique. One could argue Makuta actually succeeded in his malicious goals (taking over the Matoran Universe), while no Hero Factory villain ever has. It's the character and mind of Makuta that makes him unique. Von nebula is only out for revenge, as is Witch Doctor and other HF villains. Sure, Makuta felt underwhelmed because Mata Nui had the glory, but at least he succeeded.
That's if you don't know how to. I always found what was fun about legos was finding out HOW to use a difficult piece and feel proud that I used it for something. Not just building a figure that looks cool. Sure, coolness is great and all, but I like being proud of making something off of a harder piece. Besides, my brother uses Bohrok bodies in many of his MOCs. Just take a close look at them!
You're right on the variation, but when it comes down to shapes and how it makes characters look, I would always go for BIONICLE anyday. You get so many shapes and sizes, and you don't just use shells or the bone pieces.
Shoot, look at Matoro Mahri for instance. Sure, his shoulders are wide, but look at the torso himself. He's quite thin, and the foot piece allows for a good hunch. Wide shoulders are the only outcome of using the Inika build. But he looks more hunched or less humanoid when you use that foot to connect his head, and overall looks so unique, and it requires using less new molds.
And the pieces they use, while not all new, still allowed him to be that way. And he didn't have any exposed ball-joints. HF's torso pieces makes them upright, which, while you can add an extender piece for the neck but that kinda looks silly, is harder to pull off, and when you have separate pieces to make a torso, you can do whatever the heck you want for where the head or body goes. Moreover, the Torsos HF had to offer were one big bone piece, constraining the positions arms could be, while BIONICLE could moves things up and down a few notches, or widen or shrink shoulders (not just with an Inika torso).
Fair point, but I do like to give BIONICLE the pointers to the fact that the villains seemed unique for themselves. Sure they were clone sets. But at least they didn't loom like something from some other super-hero or sci-fi film. The Bohrok, the Rahkshi, the Piraka. All iconic BIONICLE characters. While wave 1 of Hero Factory had some pretty unique villains, after that, they didn't seem as unique and captivating as a Bohrok.
If I saw a HF villain, like XT4, for example, and compared it to the Piraka, I'd think both looked cool. Sure, XT4 has a unique build with already-available pieces, but I could argue that I'd buy the Piraka first because A) it came with new pieces at the time, B) looked intimidating and unique on it's own, and C) didn't feel like it could be from some other movie. It felt like BIONICLE. It was the uniqueness of BIONICLE that gave us the iconic villains.
Were the builds that great? Not always. But cut BIONICLE some slack. Things like the Rahkshi and Bohrok were at an early stage of BIONICLE's contraction. They were amazing for it's time. Things like the Glatorian or Phantoka had no excuse, as they came with the same builds (The Mahri are not included because that year led to some great sets once experimenting with the Inika build). Now some of the villains had some unique builds from HF, but not always. Things like XT4 were unique, but that was mixed with other not-so unique.
Overall, just because BIONICLE had clone sets doesn't mean it was worse. In fact, it gave more colors in the pieces they gave us, too, which is great for MOCing. Not to mention, like I said, many were trying to get the point in which now we have CCBS. All they had to work with was technic. And sometimes those limited pieces allowed more creativity (like the Mahri), and sometimes they were lazy (like the Glatorian). HF has the same thing happen to it. Both are guilty of this sin.