Well...they say...size isn't everything.
I have the 3124ks and LOVE it. But I read that those who have the 3326 really love the side dinette. The floor plans are somewhat similar...but you can reach into your fridge from the dinette in the 3326...for the Ketchup that you forgot to put on the table. I think...not sure but there is more counterspace in the 3124ks then in the 3326 due to the dinette taking some of that space.
Personally I think it would be cool if the 3326 had a larger shower...but to my knowledge all bathrooms are the same.
How many are you planning to sleep in your new TM??? For many that is the deciding factor.