I have never tried the MG, but I do raise the franken chickens. We range them in movable pens, moved daily to fresh grass after brooding the first 3 weeks in a barn. They grow well and do well. We feed them on average 10 gallons of feed a day (1/2 pellets and 1/2 grain), they have enough room to move around the pen, get fresh air, eat grass and we never lost any this year to heart attacks or leg problems. We butchered the first batch at 8 weeks of age, the lightest was 4.5 lbs, the heaviest almost 7 lbs. We will be doing the next batch 2 weeks later and I am guessing they will average 6 lbs.
So for me I will continue with the franken chickens, they do well by me.
Lazyfarmer, sometimes when chicks are chilled or stressed in the first couple days of life that stunts them and they never seem to recover, especially the meat birds. One thing from your comments about these birds and the rabbits you picked up makes me wonder about the quality and protein of your feed, these birds need lots to grow and that possibly could be one issue?