once your 140 get dennied, so will your 485

and possibly your legal status, if you don't maintain your H1 or other status.

With 140 pending, you probably won't dare to change job or make any long term dicision.

If your 140 is based on EB1 or EB2-NIW, then you CAN change jobs after filing 485 over 180 days, as far as it is in the same field.

Another advantage is that with EAD (as a benifit of filing 485), you are no longer limited by H1 caps.