Neither. Peanut butter, or crispy, or better yet reeses pieces. With all of the above I think it's an underrated lost skill to let them melt in your mouth one or a few at a time. You get so much better flavors from the candy and chocolate one at a time, worth it!
yuck, i wouldn't eat an m&m even if i didn't have diabetes. i never liked them. they're so sugary i can't taste the chocolate and i find the texture unpleasant. the only thing worse than american chocolate is japanese chocolate. and i do like chocolate.