I'd say the reasons were a split of personal preference and model comparison. I can't remember all of what I found, but here is what I can remember I found while researching.
Comparing models:
The current MK2 I believe is built on the E receiver which is the 3rd in the series 93 22lrs. The B22 is a whole new receiver, barrel, and bolt design. I believe the chamber has been changed to help limit the clogging of the extractors (more on this in a bit). The B22 receiver is new and the barrel is now threaded into the receive and uses a nut. The barrel in the B22 is thicker than a pencil barrel but not as thick as the 13/16" MK2 barrel. The MK2 uses a box magazine where as the B22 has new rotary magazine. The MK2 uses a larger "tactical like" knob vs the standard round end on the B22.
Known issues with each model:
In the history of the 93 series, the known issues have been, issues with the box mag (corrected), flimsy stock (can be corrected with aftermarket), slight burrs in the receiver machining when brand new (fixed with 1000 grit or cycling of the bolt), and the extractor issues (fixed by sharpening the extractor due to poor machining at factory and keeping the bolt generally clean). I could not find much on the B22 as it is pretty new.
Magazines:
You hit on part of it, the mags. I'm always dropping my 10/22 mags while removing them and they get gritty and don't work well and not too easy to clean. Also the savage rotary mags only had soso reviews while savage has fixed the issues with the box mags supposedly. I grew up with a Rem 581 which is a box mag and I could hold several in my pocket. With the MK2 I don't have the issues with rotary mags and I can put a few of the thin box mags in my pocket.
Reviews:
The MK2 has a solid amount of reviews and positive reviews at that with the only issues being mainly the cheap stock, thin magazine bottom metal, and extractor issues (caused by fouling). There are many stocks available, DIP makes replacement bottom metal and trigger guards, and the extractor issue just revolves around cleaning mainly (I shoot suppressed so already used to frequent cleaning intervals). The B22 is pretty new with not much in availability of additional stocks. The reviews out there seem positive with most saying it is about the same but costs more. (yes you did get a good deal on yours which makes it an equal).
Overall, I knew what the MK2 could do, the aftermarket part support, and it had the kinks/fixes worked out. The B22 seemed like to me to just be a fix for a problem that wasn't there. Then again this is just an opinion.