I prefer
Tessa to
Piper.
Tessa going to be less markedly associated with one generation than
Piper which has a much steeper popularity peak. They're both modern, but
Tessa has connections to
Teresa, a traditional name.
Tessa has a more subtle meaning than the direct word-name
Piper. It is also slightly more feminine sounding which I appreciate, and has slightly better associations compared to the Pied
Piper (not awful, but slightly annoying).