I haven't used a MATHS yet, but two of the first modules I got were a 4MS PEG and a Befaco Rampage, which are similar. They were both cool, but I ended up keeping the 4MS PEG and selling the Rampage. I'm not entirely sure it was the right call, but it was slightly more fun to use than the Rampage. In any case, it has been incredibly useful. I also don't see it mentioned as much when these types of complex EGs come up, so I like to throw it a mention/recommendation, bc it has been very good to me and has been a keeper from day one, where a lot of other modules have already come/gone. It has some interesting features and it's one of those tools that I use every single time I patch, almost no exceptions. And after five months or so with it there are still a couple aspects of it I need to dive a little deeper on to get the most out of (I haven't probed the possibilities of the async and qnt jacks much, or gotten all that creative with the ways its dual egs can be switched between or used to self-manipulate).
That being said, it usually actually runs a little more expensive than Maths or Rampage, and those have a few tricks that are unique to them as well. I'd love to be able to try all 3 and compare and select the one I liked the best, but for me the PEG has been way too useful to even think about trading off anytime soon. My only complaint is it can be rather "clicky" when trying to manipulate audio directly (this also seemed just as true of the Rampage, if not more so). But I mainly use the PEG to manipulate CV signals going other places, so it's usually not a big issue for me. It also may be more my own inexperience than anything particular to the module itself. ( When I first got the PEG I was approaching it more like a traditional AD(sr) which I don't think is really how its intended to be utilized.)
As for saving space with the DFAM, I recently racked my DFAM, and while it is certainly a space hog, I like it better racked and use it more when it's racked. And while it could certainly be my imagination, I feel like the audio is a little bit better too. I wondered if this had something to do with being on the same power source as everything else, but I'm not sure if that could possibly even matter, so it's probably my imagination. Nevertheless, it'll stay racked until I absolutely need the space again. I wish I could rack my Moog Werkstatt too!