JPG export has a smaller file size.

It has always bugged me as to why an exported JPG from On1 is smaller than that from other tools... while TIF or other formats exports from On1 are about the same size as those from other tools.

Of course, this has been brought up with support a few times.   

What is shown below, may be interesting to the user community.  

The original image is a NEF file at ISO25600.  The image was exported at full resolution at 100% quality from NEF to JPG in about 10 different tools plus On1 2019.

The image on the left represents that of about 10 other tools.
The image on the right shows the export of On1.

(I can't explain the difference in apparent size while at the same magnification. Multiple compare tools show this same discrepancy with the On1 file. I am choosing to ignore that for now.)

The difference in noise signature of the two files is interesting. 
From observation, the On1 JPG export  has less noise.  Not a show stopper, but generally noise reduction is something the user typically has the choice to turn on/off as NR can impact image clarity.  

It is also possible that it the noise reduction comes in the initial RAW file import.  Oddly, the native view of the NEF in On1 is different from both of these export examples. 

Obviously, ISO25600 and 350% zoom is a bit pathological.  This same result shows up in more mainstream settings, too.  This example is given as it is easier to see. 

If you only use the On1 tools, this may not impact the workflow.  If you have an external noise reduction tool, it may be worth considering what happens between On1 reading the RAW file and the JPG export. 

It may also be worth considering what happens during export after editing.

Bottom Line:  It seems On1 JPG export always reduces noise even when NR is set to off, thus impacting (reducing) JPG file export size.