For me, 'Girl Friends' stands out. The art is great, and the relationship between the characters is very engaging. It also explores various emotions and challenges in a realistic way.
I think 'Citrus' is one of the best. It has a compelling story and well-developed characters.
I'd recommend 'Kase-san and Morning Glories'. It has beautiful illustrations and a sweet, heartwarming plot that makes it a top choice among yuri manga.