.jpg export quality

Ps and LrC use the same 13 Quality settings, but with different number scales as follows:

(JPG Compression)

Photoshop        Description       Lightroom

0                      Low                  0-7

1                      Low                  8-15

2                      Low                  16-23

3                      Low                  24-30

4                      Low                  31-38

5                      Med                  39-46

6                      Med                  47-53

7                      Med                  54-61

8                      High                 62-69

9                      High                 70-76

10                    Max                  77-84

11                    Max                  85-92

12                    Max                  93-100

From LrC you may be 'exporting' from a raw file render to JPG.

From Ps you are 'saving' from a pixel RGB image to JPG.

So there may be differences, but the major factor is the 'Compression'.

JPG COMPRESSION EXPLAINED by Jeffrey Friedl

But the loss can be negligible, and sometimes JPEG is the necessary format depending on the intended use.

I only use jpeg for web use. For my design and photography work i export as either a PSD or Tiff. Jpeg is a compression format and you will always lose something when doing a JPEG.

You always lose some quality when exporting as a JPG. There is no way to avoid this if you want as JPG. It's not different between Photoshop and Lightroom Classic.

If you export as TIF, then you should not lose quality.