Flex and Momentum are pretty much the same thing. Momentum was the overall program. Flex was counting Points. Whereas Core was eating only foods off a certain list and listening to hunger signals.
There's certainly nothing wrong with sticking to the old program if that's what you want, but I have to wonder why you're not even going to try the new program first.
There really are plenty of people who are losing weight quite successfully on PointsPlus. I do suggest going to meetings for a while to hear about the plan if you're at all curious.
Best of wishes to you and your husband on getting healthier!
~Made of star stuff~