Mohara, you know how in ice cream they will offer several different vanillas including French Vanilla, Old Fashioned Vanilla, and Natural Vanilla,among others, and even though they are vanilla they have a bit of a different taste. I, personally, like DH French Vanilla, and that's what I use along with the French Vanilla instant pudding, but really it's a matter of personal preference, and which ever one you decide to use, it isn't going to ruin the cake. In fact, I sub sour cream for the yogurt, again, a matter of personal preference. You could actually, use any flavor of cake mix and instant pudding you wanted to use. It would still be a good cake, just a different flavor.
Just another thought, I think the Almond Cream Cheese Pound Cake, first CMD book, page 129,(you could change the extract flavor if you wanted) would be a good candidate for French Vanilla cake mix. But there again, almost anything is good with cream cheese, when a person likes cream cheese.