Most two-piece systems consist of an ordinary open gutter with a gutter cover, gutter guard, or gutter screen installed above or on top it, attached either to the gutter itself or to the roof of your home. This means that it is not fully seamless which could cause leaks to occur.
Since the gutter and gutter guard or gutter cover, are separate, this could make the fascia and soffits of your home vulnerable to water damage.
If you install a gutter guard or gutter cover under the shingles of your roof, debris that did not slide over the guard or cover, can become trapped, causing build-up and clogs, which can cause more damage.