It's rare to find even one type of aka uni in a sushi course, although if you're at a high end sushiya between June and late September there's a decent chance you'll encounter it. Aka uni is smaller and more delicate than even bafun uni, and doesn't travel nearly as well, especially outside of Japan. The flavor is less uniformly sweet than bafun uni and oftentimes, notably smoky.
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Unfortunately, these pictures were from almost a year ago and I didn't take detailed tasting notes or other facts on brand/origin/etc (@bootsy_gi who was with me, might remember better). What I do remember is that all three varieties were absolutely pristine in texture and flavor, with distinctly different notes of sweet, smoky, and briny flavor. I am pretty sure the one on the right (with the most nondescript box) was my favorite, coming from the Yamaguchi area. This was a type I only had the opportunity to enjoy once before when I was in Kokura back in 2017, so it was pretty special to encounter it again.