Boris Cabrera didn't match much lookwise, but at least he had some moments of decent acting; the Visser One arc moved me from "who IS this kid and where did he put Marco?" to "okay, fine, he needs to lay off on the hair gel but I can live with this". Compared to all the other kids, who ranged from having no screen presence at all like Nadia Nascimiento as Cassie to being some of the most wooden actors I've ever seen on television like Christopher Ralph as Tobias, Boris Cabrera was an okay pick. That said, it took him about ten episodes to realize how to deliver a comical line, so it's not like he didn't suck at the beginning. I'd much rather they go by acting ability than by "look", because Brooke Nevin is just an awful, awful Rachel to me.
I actually really liked the actors who played Peter Jeremy, Visser One and Cassie's mom. They still were dealing with an awful script, but it's kind of like they could turn garbage into gold. The scenes with them are easily some of the strongest in the series, and they tended to bring out better acting in the other actors too.