When using the Post-Crop Vignette panel in the Develop Module in Lightroom, if you prefer Color Priority or Paint Overlay (instead of Highlight Priority) to be the default style, you can change it by customizing the Develop module’s Default Settings.
This video, Working with Camera Profiles, explains how to customize and save new default settings in the Develop module. Because the video was recorded when Adobe announced Camera Matching profiles (in LR2!), the first six minutes of the video discusses these profiles. However, it then it goes on to explain how to set your default settings in either Lightroom or Camera Raw and even though a lot has changed since then, you can still use the same method today for changing default settings for panels other than Camera Calibration – including Post Crop Vignettes and Lens Correction.