I woudn't say either of them are underrated, but my favorite Elphabas are Danna Paola, Rachel Tucker, and Julie Reibler. I've seen Julie, Dee Roscioli, Stephanie J. Block, and a young Eden Espinosa. I think Caroline Bowman's Elphaba was too shrieky, but her Eva was fabulous (saw Evita twice!).
"I saw Pavarotti play Rodolfo on stage and with his girth I thought he was about to eat the whole table at the Cafe Momus." - Dollypop