My experience like others is that the Tessar's aren't as sharp as the Xenotar or Planar until well stopped down. I use a lot of Tessar (or Tessar type) lenses and that's the norm across all formats.

If you need critical sharpess other tahn well stopped down then a Tessar os not ideal, and the Planar is of older origin but until coating was prone to far more flare

Ian