While my son is set on whom to ask for his Special Interest recommendations (the music director of our area’s youth orchestra), he is undecided on whom he should ask for his Personal recommendation. One possibility is the person who helped prepare him for a coming-of-age religious ceremony, and who has expressed great admiration at how my son prepared and “performed,” and who admires my son’s continued participation in weekly services. The other is my son’s Mandarin Chinese teacher, who has taught my son outside regular school for about 10 years, who really likes him, and who appreciates how he has been able to move forward with the language despite his parents being Caucasian and having no background whatsoever in Chinese language and culture. Assuming the recommendations were equally positive, which person’s would impact my son’s admission chances most favorably? Thanks for any insight or opinion you can provide!
Submit both 
If you can send both, do so. But usually you are limited to one personal recommendation (or none). In that case, assuming they are equally positive, send the one who has known him the longest.
Good advice from @Altras. (Some schools specifically say NOT to send extra recs, so just be mindful of that.) Another way to choose would be which recommendation will add dimension to the application. In other words, choose the rec which will not have info repeated already elsewhere in the application.
Thank you all so much for your time and insight! Much appreciated.