sprout is like an expanded version of Giri koi
a girl falling for a popular sporty supposedly charming
guy who happens to have a cute little clumsy girlfriend
and can't make up his mind who he really likes ..
the girl is a whiny crybaby who can't give up and move on ..
Both stories deal with a girl going to a new school and not knowing anyone, and then finding someone/people that bring them into the crowd. Boyfriend has a little darker..."drama" in my opinion. Although the drama aspect of the story may be different, if you liked Giri Koi you'll like Boyfriend.
Both to me had a similar "feel" to them because they were both REALLY CUTE and about a girl who doesn't fit in at first in her school at furst but after meeting and becoming friends with nice guy she starts to make lots of friends and have a normal school life that is until things get complicated...i really think that if you like one of these mangas then you will like the other one :)