You mean just intonment vs. equal temperament?I guess not. I thought well-tempered and equal tempered refered to the same thing. So are pianos most commonly tuned equally? I tune my own piano and this is new to me.
found an article on temperament entitled 'good vibrations' by ruth franklin. it's a good read when you have time:www.tnr.com/121001/franklin121001_print.html
I tried a few temperatures with my stage piano. The well-tempered ones (Kirnberger 3 and Werckmeister) really sound better for the Waldstein! I also noticed a big difference in Mozart's sonata facile.Good information page: https://www.kirnberger.fsnet.co.uk/