I also love both brands and I wear both brands regularly. But if I only got one foundation for the rest of my life I would definitely go with MUFE. I think MUFE is ahead of the game in terms of formulation and technology, and it looks much better in photos compared to MAC. MAC is catching up, as I think their 2 most recent foundations (Studio Sculpt and Pro Longwear) have been their best by far. Most all MAC foundations broke me out in the past (I'm looking at you, Studio Fix Fluid!), but that hasn't been the case with their newer foundations. However, there isn't a foundation that I would NOT recommend from MUFE. They are ALL of exceptional quality, whereas there are several MAC formulas that I would definitely stay away from! But obviously, when it comes to foundation it really depends on the individiual's needs and skin type. Your mileage varies so much with foundation, so the best thing to do would be to try it out first if you can. Just because I think MUFE have the best foundations currently available on the market doesn't mean that you will find one that works for you!
My first recommendation would be to try MUFE HD, its the best all-around formula IMO. If you feel the coverage is lacking, you could mix it with a small amount of concealer. But If you have dry skin, you might want to also try MAC Studio Sculpt. Good luck in your search!