[次第「じだい」]だ => It depends on A N2
Based, Focused, Depending on
[次第「じだい」]では => Depending on A, B may change N2
Based, Focused, Depending on
[一方「いっぽう」]だ => Change A continues, A does not stop N2
Miscellaneous
[一方「いっぽう」] => On one hand A, on the other, B; Although A, at the same time, B N2
Contrast,Surprise