The New York Yankees and Boston Red Sox rivalry is one of the most profound rivalries in all of sports. With hundreds of years worth of competition with tensions rising far higher than the boiling point, this is a rivalry that defines baseball and transcends sports in its entirety.
However, the Red Sox and Yankees rivalry also has fans of both teams going at each other over which team has the brightest future. At the end of the day, both fanbases want bragging rights for years to come over their inferior.
In any case, when comparing and discussing prospects, it makes more sense to compare positional players to fellow positional players, likewise for pitchers.