PGP isn't any better on the first point and on the second point, I would bet the money in my pocket that GPG (being the most dominant implementation of PGP) is far more complex and bug-ridden than Signal's cryptography or implementation are unsound.
GPG is an implementation of the OpenPGP standard. Signal Messenger is an implementation of the Signal Protocol quasi-standard. Comparing like to like, OpenPGP is much less complex than the Signal Protocol. GPG is much less complex than the Signal Messenger.