Often I'm limited by email hoster size limits. Eg- my email won't let me send an email over #Mb, or I can't upload a pic larger than #kb.
I'd love to have a resize option "Resize to:" And then "Less than #Mb, or less than #Kb, etc., and then have the program decide the parameters to give me the best quality I can get for that file size.
I keep a resizer program just for that purpose.
Using the other options (percentage, height/width, etc. I'm always guessing. If I guess wrong and the final file is too large, then I have to do the whole thing again. And with batch processing? Forget about it.