Another consideration is where you're coming from. We fly into DFW from AUS all the time. With the two cities being only 200 miles away, we usually don't experience any major delays cutting into our connection time. However, if you're traveling into DFW from farther away, that adds in more uncertainty.

We have done 1 hour layovers lots of times through DFW with two parents and 1 and, now, 2 children. nbd. No time to dawdle, but it's not too stressful, either. We usually have enough time for a diaper change at whatever family restroom we pass along the way.

If the baby needs to nurse between connections, then the 3 hour layover might be preferred. It's easier to nurse off the plane where you can spread out. The Kids' rooms in the Admirals Clubs are great for this.

The one caveat I can think of is if the layover is going to take place when the baby normally naps. If you have a flexible kid who can handle nodding off a little later than usual, then go for it. But if you've got one who sticks to a routine and would end up taking half or a third of a nap while transiting through the terminal and then being fussy and tired but awake on the flight, that might be a factor.