I just want to confirm that I am NOT saying don't go on a new med, there might be really good reasons, benefits to it.

But your doctor should be able to tell you why they think the new/unproven med is "better for you". And if they can't do that then I would really proceed with caution.

I've been taking Metformin for exactly 20 years now. My kidneys are fine, taking creatinine tests every 3 months. I take Tresiba for the past 6 months. I see no difference between it and the Lantus I've been taking for years before.

Metformin is safe.

It has been prescribed for over 70 years (although only since the 1990's in the US). With that length of use they know all the side effects and if it was dangerous, caused cancer or other serious problems they would be well known by now.

Tresiba on the other hand was only approved in 2015. They have no way of knowing "what" side effects it may cause after taking it for say 10 years. It might be great or it may be like a few others that were approved over the past 20 years that were taken off the market when they found they caused serious side effects a few years after they went into wide use - a clinical trial often lasts less than 3 years, so they can't tell what long term use will do or if taking it even for a couple years will cause some problem 5 or 10 years down the road.
(NPH has been around for decades and Levemir has been around for almost 20 years - both are examples of "similar" to Tresiba)

If "my Doc" suggested one of the new drugs (less than 5 or 10 years on the market) they would have to give me a list of positives that greatly outweighed the drugs that have been on the market for 50 to 70 years that (we) know won't kill us...

No it is Not. That's why my kidneys are bad and I was on details. I would Not recommend Metformin

I take both, Tresiba for 7 months now and Metformin for 20 years. Metformin can cause diarrhea and nausea at the beginning and for a short time and kidney problems in the long term. I had neither.

Tresiba is working better than my previous long-lasting insulin Lantus. It's effect last longer and my night numbers are lower.