I personally really liked the style Stuart Sayger used for 06-07. To me, it fit the darker tone really well.
(NOTE: Hijacking this thread to make a poll because I think this question fits that the best. Feel free to discuss in the comments like normal, though! - Kahi)
I think all of them sans Sayger were pretty good, I collected a bunch around 04 but I have a lot of good memories of the last few Leigh Gallagher comics as well as all of Pop Mhan’s (though the script for the last Bionicle comic was garbage)
Zanier’s work in the Graphic Novels is amazing. it is like looking at pictures of the sets. I specifically like how he portrayed the Baterra (the most amazing things to come from Bionicle).
My personal favorite is Sayger, if only because of nostalgia. I remember the days when I’d just gotten into BIONICLE, and I’d sit on the couch and read the comics over and over, trying to catch every detail.
I really liked Stuart Sayger’s style for the most part, but here I just had to go with Christian Zanier. His work was just phenomenal and I wish he could have had more involvement with Bionicle.
I really love how detailed Christian Zanier is. His art style is definitely my favorite. Sayger would have to be second because he drew some of my favorite panels in all the comics. Though it did get a bit, odd at times.