Okay, bad news. No wait, good news? Weird news. I'm starting to like my Maruszczyk Jake more than my Sandberg, maybe, I'm not sure. And I have to kinda change my observation that I get an ever so slightly lower action on my Sandberg, they are actually close to identical now and I'm not sure what happened. Maybe the Maruszczyk just needed some kind of "break in" period? I'm not sure how that works but it now plays pretty much identical to my Sandberg after lowering the action a bit and there's also no buzz.
I also swapped strings on the Maruszczyk to Newtone roundcore nickel roundwounds and I love the sound of them.
Now that I think about it, getting used to the Jake or maybe the neck settling some more could explain why I could lower the action a bit more, and the fresher (and different) strings could explain why I currently play it more.
Anyway, the result of this rant is that I'm now very much interested in a custom Maruszczyk Frog, probably headless and very fancy, while I was thinking about buying a Sandberg Basic before. Either purchase is still far into the future, but having more options is both great and kinda annoying.
I also wouldn't say no to another, almost identical Jake. Maybe with Haeussel pickups instead and flatwounds.