ColorSync Utility is what your looking for. For me the standard compression was also too little resolution & too lossy compression. So I created a new filter in ColorSync - which then becomes available in e.g. Preview: Resolution 200 dpi, jpeg quality ~75%
Step 1: Open ColorSync Utility & create the new filter such as below
The above settings give me files with acceptable size and decent quality (e.g. for sending by e-mail)
Step 2: Open the PDF in Preview, then choose File > Export, Click the Quartz Filter pop-up menu, then choose the relevant filter ("Reduce File Size 200dpi" in this case)
