When I shoot stills either for my clients of for myself, I shoot in RAW format. That way, I can manipulate the base image and have it look any way I want it.
But once I finalize the picture(s), I usually output them in JPG format. Most of the printers I deal with require that format, and if the pics are for web display, the best format is either JPG or PNG. And though JPGs are a lot smaller than RAW images, if you shoot and store enough of them, they can take up a significant amount of space.
Which is where JPEG Mini comes in. It basically strips away all non-essential information from the file, and just leaves the image behind. How good is it? How about routinely reducing your pictures to one quarter of their size? Or maybe even smaller!
I'm not getting anything out of this. I just think the program is an excellent product, and if you shoot a lot of pix, you'll probably wind up seeing the benefits of using it.
There are two (really, 3) versions of the software. There's the personal version, which handles smaller files as a stand-alone program. A free version of this software does up to 20 pix in one day. If you pay for it, it's only $20. The professional version of the software crunches pix up to 8 times faster (which can be a help if you've got hundreds – maybe even thousands – of pix to squash), and works in stand-alone mode and also works as a plug-in for Adobe Lightroom 5 and above. That version is just under $150. JPEG Mini is available in both Windows and Mac flavors.