Ni Ten Ryu combines many styles of martial arts, such as Karate do, Aiki do, Hapki do, Kung Fu and any others. The philosophy behind this is that no one style is better than any other, but that the differences can be used for differing circumstances. For example, many Karate techniques are very confrontational and direct, resulting in a very powerful and fast style. Most Aiki do and Kung Fu techniques involve circular or evasive movement, often seeming slower and more graceful yet building up great momemtum and conserving energy.
Students of Ni Ten Ryu endeavor to learn as wide a range of techniques as possible, to have a large "armoury" on which to draw. Part of this philosophy means that a student must always keep an open mind to new techniques or styles. Inevitably, individuals have their own favourite set of techniques, this is the student developing their own way based on that defined by the school. There is nothing wrong with this, as long as the student learns and understands those techbiques that they dont' like as much as those they do.
Musashi puts great store by learning many things, not specialising in only one thing. There are things of value to be learned from all forms of study, and many surprising applications. For example, the rythms of music or poetry are echoed in the rythms of combat.