I have a 17'6 tracker deep-v and I put on a 24v 71# motorguide /5 speed. I hated that thing; even at the lowest speed it was just too fast. The key problem here wasn't the 24v but the 5 speeds. I believe both of these motors are fixed speed motors. I sold that thing after a year and a half and put on a 12v digital motorguide tour. I still run 2 batteries and for me the 12v is a better choice. Spend a few more dollars and get a variable speed, you'll be much happier. Brand doesn't matter if it's MG or MK is a personal choice. I personally like a cable steer so I wnt MG, some guys like the power drives but as long as it goes where you want it doesn't matter, it's a personal choice.
Do a search here, lots of guys trying to slow down 70# fixed speed TM's. They suck on light boats.