I haven’t met a meatball I didn’t like, but Mexican style albondigas are my favorite, whether in soup or in salsa, and for me (or as I’ve been doing lately, in a Mexican style meatball sub).
For me, the essential element in sopa de albondigas is the herbs. I use mint and cilantro in the meat, and oregano, thyme and marjoram in the broth, and the only chiles I use are roasted jalapeños which I add at the end as a garnish. For binders in the meat, I use raw rice and a little bit of coarse masa harina. Usually I go for 80% lean beef, but this time I used 73% and it was perfect,