The basic plot's the same: Naive schoolgirl has an unrequited first love for the cool, dark-haired guy but he already has a beautiful girlfriend. However, unknown to the girl, he likes her back too? A second love interest appears as a classmate who holds an unrequited love for the main girl. Even though he knows she likes someone else, he wants the chance to be with her. The love triangle turns into a square.
The characters in both manga have depth to them and are not just the typical rival girlfriend or typical male second lead. At first, both manga seem like generic shoujos but as one reads on, they deviate from the usual formula. There's a similar pastel-like art style in both of them!
The "winning" guy of Strobe Edge is not the same as the winner of Tonari no Atashi so if you were dissatisifed with the first love/second love not ending up with the girl, try out the other manga.