What cartridge for a prime super scout 10.5 arm.? Budget $500

For the money you want to spend-
https://www.lpgear.com/product/ATOC9III.html
Just $50 more.
AT OC 9 series has been around forever, and a solid choice for the price. Your phono stage(in your case it's part your Mac?) plays a big part in how it performs.

The latest version will be easier to mount(body is threaded)
https://www.lpgear.com/product/ATOC9XML.html

https://www.sound-smith.com/cartridges/fixed-coil/otello

I have used both with my VPI, not the latest AT OC9.
My guess comparing the old with the new will be negligible (very subtle)at this price point/your gear.

To my ears the Soundsmith had a more convincing midrange at the expense of a less bass(still there, just not as dynamic) It can be rebuilt by SS, and last forever.

OC9 had a more overall more dynamic, but maybe tipped up higher end.  

Only your ears will know. YMMV.

Try the Hana SL I believe, for $450 is a great cartridge 

With your red line at $500 you’d better look for vintage MM carts in NOS condition. Nothing can beat’em if your limit is $500!

If you did not learn the lesson with Sumiko you can buy an MC, but I think you need something with user replaceable stylus (and this is MM).

The Hana SL retails for $750, but can be found for less. 

I appreciate all the recommnations.  When I first went to order a cartridge after the receiving  the VPI, I called Upscale audio for recommendations. I told them my price point and they recommended the Sumiko Bluepoint No 3 & the Hana EL. They said either was a tossup with the Sumiko being easier to mount since it's threaded. I would like to try the Hana SL however it's above my price point. I'd like some more recomendations in my price range especially from real world VPI owners. I'd also like to know what the sonic differences are between MM & MC especially since my Mac C50 can take either one. My audio dealer who did a great job installing and aligning the Sumiko said that he's had good results with Denon cartridges. Any thoughts on those?