I had the 2016 15" MBP, and I have had the 16" M1 Pro for a week now. I thought the 2016 MBP was the worst Mac laptop I ever bought ( I have been buying and using Mac Laptops since 2002). The reasons I did not like the 2016 MBP were:
The keyboard was horrible to type on (1st Generation Butterfly)
The fans would come on when exporting video or playing games
I did not like the Touch Bar as it was too easy to hit the virtual ESC key and lose what I was typing and I had to look at the keyboard to use it ( I can touch type).
Dongle hell - I had to use dongles to connect to video projectors, and external displays.
I had been using a M1 13" MBA for the last year, so I do understand the benefits of portability from a smaller laptop, and I take my laptop to work every day as well as use it in meetings and conferences.
The new M1 16" MBP solved all of the issues I had with the 2016 MBP, its the best Mac Laptop I have owned to date. However the 2016 is noticeably heavier than the 2016 MBP and obviously heavier than the 2020 M1 MBA. I do miss the portability of the MBA, but the screen and performance of the 16" M1 Pro outweigh the downside of the additional weight. I have not heard the fans once in the last two weeks.
You will probably be fine with the M1 Pro, here are my benchmarks comparing the 2021 MBP with my slightly newer that your 2015 MBP. You will notice a huge improvement in performance. I can remember when I got my M1 MBA, it really was night and day the difference in heat and performance with my Intel MBP 2016 that it replaced.
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