II love, love, love Primo's buttermilk bar. And when their cinamon twists are warm, they are so delicious - soft, sweet, fragrant. Overall, I'd say Primo's wins because even their worst donuts are still pretty good, however...
I did a Primo's vs Royal Donuts cinamon roll and coffee taste test a couple weeks ago. Much to my surprise, Royal came out on top in these two categories.
Looks: In a side-by-side, Royal's cinamon roll looked burnished and generously-sized compared to Primo's pale speciman. Primo's roll looked a little sad and wan.
Taste: Royal's was crisper, more caramelized and deeper flavored. Primo's was okay, but in comparison, bland and had more of an undercooked doughy taste.
Coffee: Primo's is too weak and clearly from some industrial Sysco-type brand can. They offer it for convenience, but on average, it's better to skip it. I think Primo's only has non-dairy creamer. Royal's coffee actually tastes freshly brewed, it's of normal coffee strength (i.e. not watery), and they have actual dairy creamers. I'd say it was as good as Coffee Bean across the street, and like half the price.
Royal also does a mean apple fritter, which I have yet to see at Primo's. (next, I'll have to do a Bob's vs Royal apple fritter test).
But the rest of Royal's donuts are somewhat uninspiring. The rest of Primo's are consistently decent, sometimes transcendent if you catch them while they're hot.
Also, ambiance wise, Primo's blows Royal out of the water. Primo's is bright and clean. Royal is probably clean, but it's dark and has the kind of decor that your neighborhood wino would feel comfortable in.
But if I want a cinamon roll, an apple fritter or coffee, Royal every time.