Both manga are essentially slice of life stories woven carefully around exciting baseball action and subtle romance between childhood friends. If you liked one, chances are you'll love the other.
If you are a fan of Adachi Mitsuru or even sports manga in general, both of these are a no-brainer. Both H2 and Mix focus on the friendship and rivalry between two talented baseball players, while using the sport aspect not as the main appeal, but instead as a catalyst for developing the romance sub-plots. There's a certain relaxing charm to Adachi's manga that you won't find elsewhere. He also has a... let's say, "quirky" sense of humour.
By the same author, Adachi, Mitsuru has made baseball into the normalities of everyday life and makes it unique. Baseball with all it's trials, errors, and hard fought battles with a great twist of romance.
if there was anything that is similar in terms of manga it is these two series. is like the author just took the original title make changed the name... well not quite that similar the plot are a little different. i have trouble remembering which scenes came from which series.
They are both romance type relationship, except one has sports implemented. The similarity between the two is that the protagonist is halted at the same crossroad, choosing one woman or the other. If you like this one, you are sure to like the other.