Cartridge for vpi Aries scout with jmw9 tonearm

The mass of that arm is 10 grams. Any Grado is a good match with that arm!
https://gradolabs.com/cartridges/

I ran an AT OC 9 on that arm and loved it!

I’ll second the Grado suggestion. I purchased an Aires 1 deck w/ JMW 10 in 1998 and used it as my primary and then secondary deck for several years. I already had a Grado The Reference cartridge and mounted it. Sounded great. I tested several other MM and MC cartridges over the years and always went back to the Grado. Detailed enough, warm and musical. My advice is to purchase the best Grado cartridge you can afford or fits your budget.

If you're looking for Grado try to find Joseph Grado Signature XTZ or another similar grado cartridge body and XTZ stylus (available separately). This is the best stylus for Grado. 

However, i must say there are better MM cartridges than Grado for sure. 

You should look at the Hana ML. It's a great sounding MC cartridge that punches way above its $1200 price point. You didn't mention your budget but Hana cartridges start around $495 up to $1200 for the ML.

When I had my Scout I used a Transfiguration Spirit and a Nagaoka MP-500. Both  worked very well on that table. If I remember VPI seemed to like Dynavector cartridges for that table. Good Luck!