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?

Consider  a Nagaoka 
MP-200. MM.

Most NOS carts are old tech, Ancient history.

+1 for the AT - OC9XML for $549. Nude Microline stylus and boron cantilever. 

The Nagaoka are the most satisfying MM carts I've heard yet.  MP200, 300, or for the ultimate in refinement...MP500.  

I see the  AT-OC9XSL getting a lot of love in the reviews. While both are a bit out of my price range, I wonder how the Hana SL and the  AT-OC9XSL would compare? I like a lively and bass heavy sound. Not really looking for a laid back reproduction. I will have to give the Nagaoka line a look although with the ability to use MC carts, is there a reason besides cost that I should be looking at MM?

 

The Nags will give you what you want. You might also consider the Audio Technica VM750SH. I have one on a second system and it’s clear, detailed, and dynamic especially at low volume, and tracks perfectly with almost no vinyl noise.

is there a reason besides cost that I should be looking at MM?

Yes. One less amplification stage to get in the way of the music and more importantly, MCs at the lower price range are not necessarily any better than MMs.
Curious, why not get another Sumiko? What do you hope to improve upon?

Good question regarding why not get another Sumiko. I figured why not try another cartridge since there are so many out there. I thought the Sumiko sounded fine, however what am I comparing it against? I still have the body and I can perhaps get it rebuilt and have as a backup.  I asked earlier about the Denon but I haven't received any responses on that yet. The reason I mentioned it is because my dealer who installed my Sumiko said that he has installed a Denon L110 on a VPI for a customer and it sounded great and it's in my price range. The VM750SH also sounds interesting. Not an easy decision to make

My first MC,

Audio Technica AT33PTG/II, ML on boron, $50. over your budget

excellent sounding, tight channel balance and wide separation.

https://www.audio-technica.com/en-us/cartridges/type/moving-coil/at33ptg-2

you can get just in your budget here

https://www.ebay.com/itm/254980772116?epid=27032781048&hash=item3b5e09d114:g:yjsAAOSwQVRebF4a

My friend had a NOS Goldring Eroica LX, no way to play MC, gave it to me, I have 3 tonearms, we can compare cartridges quite readily, it sounds excellent also, just in budget, however I think the AT fits your stated preferences.

https://www.ebay.com/itm/254804394240?hash=item3b53868100:g:Yq0AAOSwVH1f0qF5

MM

I also still like the sound of my MM cartridges, Shure V15Vxmr body with a new Jico SAS stylus on Boron, and actually prefer my lightly used AT440ML ML on aluminum to it for some content, primarily it’s greater separation over the Shure. The current model is 540, here with a spare headshell, under your budget, replaceable stylus in the future, ML on aluminum

https://www.audio-technica.com/en-us/cartridges/type/moving-magnet/vm540ml-h

AT has other MM that cost a bit more still in your budget to consider.

The Sumiko Blue Points are tried and true. The number 3 (have not heard one yet) is just the latest iteration in the line. I had a 2 in my system while my Lyra was being serviced. It’s a fine cart for less than 500.00… I’ve played with others (Clearaudio, Ortofon, etc.) the Sumiko is the one I would go back to. The others were fine, but I liked the Sumiko the best for what it was. 

If your willing to try something other than a new cartridge ,
I'd recommend a Fidelity Research FR 101 or if you can find it a 101SE .
For less than $200 you can have a top notch cartridge .

Have Soundsmith rebuild the cartridge, I had a BP evo3 done by them and it sounded excellent or buy the best used low hrs Soundsmith you can find.

Soundsmith otello

The Otello was also my list when I ended up purchasing the Sumiko.  Still looking for someone who has tried the Denon DL110