Either one is fine. You could even chose them in T.P.O. 私は<formal>： for essay/composition, for the office, for any official situation 僕は<casual>： in lyric(poetry), for any age group; however, its prominently used by tween - minor There are some more vocabularies that mean the same as 私は/僕は Just FYI, 私は (formal) for men& women 僕は (casual) for men オレは　(informal) for men 自分は (neutral) for men& women <-- I often use this わたくしが (very formal) for men& women

私/僕 なら、どちらでも問題ありません。 普段は「僕」、少し気を使う時は「私」で良いと思います^^ 頑張って下さいね。