。
Of these, the important one is the latter.
Literal
This among important [nominalizer-の][topic-は] latter [possessive-の] side [copula-です].
後者 'the latter (one)' is the standard formal way to refer to the second of two items just mentioned (paired with 前者 'the former'). 方 (ほう) here picks one side from an implicit comparison. The polite です ending keeps the register conversational rather than academic — the same proposition could appear with である or copular な in stiffer prose.