Handheld electronic devices and methods involving improved antenna performance are provided. A representative device includes: a housing; a first antenna mounted at a first position of the housing; a second antenna mounted at a second position of the housing; a hand position monitoring system operative to determine a position of a hand of a user grasping the housing of the device; and an antenna selection system operative to selectively and alternately activate the first antenna and the second antenna such that, responsive to the hand position monitoring system determining that the hand is in a vicinity of the first antenna, the antenna selection system activates the second antenna, and responsive to the hand position monitoring system determining that the hand is in a vicinity of the second antenna, the antenna selection system activates the first antenna.