You'll hear both, and IMO it really depends on your partner height. Tall partner, you can get away with the ribcage connection and gain more freedom in the legs. Short partner, you need a lower connection to get more "volume."
I agree that both are correct. It depends on the partnership.
Personally, I use a high connection (lower to mid ribcage only). I only move to a lower one when creating a big shape in a pose... trying to use it the rest of the time, I feel stuck and like I have no space. If I had a partner that was taller than me (rather than working with someone about my height), I'd have to move the connection point lower to make it feel the same.
There is of course no single correct answer. Dancing is not an exact science, so it's not about absolute truth but about teacher constantly correcting their students. So even from the same teacher you can hear totally opposite descriptions, depending what they want to correct
In my case, my connection was generally higher in the past than now. Recent teachers tried to make us aware of different roles of lower and upper body, introduced terms like upper center and lower center etc. Lower body is the motor of the couple so you need to feel connection there. Big part of leading happen in hip / thigh area, like opening the partner to PP, closing her etc ... Upper part is for the shape and can have quite different role. However, you need to feel the strong right side of the partner and lady needs to make a shape with upper part of the core (not from the waist) to avoid balance problems, so connecting area extends upwards to the ribs - unless of course in poses when flexibility of the spine (which is varying a lot among ladies) isn't enough to achieve it ... and it can move from right to left in some figures etc ...
Both are correct. I teach both. It really depends on which school of thought your teachers have learned from. Some call it the old Russian style and some refer to the lower rib cage and higher connection as the Italian style.
OP, this raises the question of the relationship between your instructors. I take lessons with multiple teachers, but it's an environment where I feel free to ask about differences. That gives them a chance to explain why they might have different recommendations, and, if it is situation dependent, to explain that as well. Doesn't work if there is not professional respect and a lack of jealousy.
I see high level dancers with a lot more freedom at the hips than I am accustomed to. I realize what I've learned is oversimplified.
Recently an out of town teacher said the contact point changes constantly, that there is not one single point of contact. That may be the same as what earlier posts say. That was a new concept for me, as I had tried to maintain hip contact throughout all figures. (Even though I knew high level dancers were often not conjoined at the hip.) Specifically, from about my hip bone to lowest rib matching his hip joint to waist. (On me, what I call "hip bone" is 3 inches above what I call "hip joint".) For me, the rib contact was coincidental, not intentional. Also only recently did I become aware of the rib contact leading movement isolated from what the hip contact leads. Before I must have been following that only from instinct, or perhaps leads were silently frustrated with my simplistic following. Now I find that high-contact/low-contact additional dimension to the lead fascinating!