I have been on both Imagination and Enchantment. I'm a 32 year old male. I rate the Enchantment the better ship hands down. While the Imagination may have a younger and slightly wilder crowd, I believe this varies from week to week. In my opinion and according to my tastes, RCCL's food far surpases that of Carnival. The disco's are equivalent and equally lively. Whereas I don't believe your brother would be disappointed on either ship, especially since its his first cruise, I think Enchantment would be the better choice for overall cruise quality.