Let me ask one question, which plane would you be safer in?
I believe it is the plane that you practice in and passed your check ride in rather than the other plane. If you passed your check ride in the 206 you will be a safer pilot in the 206 then even in the 172, because you trained for that plane.
There is really no right or wrong answer in my opinion, because their are good pilots that have taken both paths. If you really do not know what you will be flying, fly the 172, it is safe, cheaper and tried and true.
In my opinion, if you know what plane you will be flying after you get your ticket, one should practice in that plane that s/he will be flying in.
It is cheaper and safer in the long run.
When I was getting my pp by happen chance, I met an old salty pilot at the fbo and we started talking. He told me in not so many words that I should "seriously" consider being taught in the plane that I am planning on flying. If I am planning on flying a retractable gear plane, then I should learn in a retractable gear plane. Same thing with the constant speed propeller.
I am glad that I listened to him. It was really easy to learn because it was just one more thing to remember in the check list. You will not be spending your time and money in a plane that you will not be flying.
You will still need about 25 hours in make and type to be considered really safe, so get that time with instruction with a Cfi in your right seat. Especially if that is the main plane that you are planning on flying. Your CFI will answer every question and ask questions that you did not even think about asking.
I think it is safer to practice stalls and maneuvers in plane that you will be flying because you will know that plane's particular characteristics and if you happen to have a stall, you will be safer having it in the plane
You will be a much safer pilot in the make and model you get your ticket in.
On a personal note, I think it is better in the long run, to learn in a retractable gear plane, especially, if you ever plan on flying a retractable gear plane in the future. You will have the great (good) habit of always checking to make sure the gear is down, even when distracted. Because that is how you were initially taught. It is the rule of primacy, you do what ever you were taught first, good or bad.
I would like to see the data on gear up landings and my guess is that there would be significant more gear up landings in pilots that were taught in fixed gear planes first.