I would highly recommend against EITHER. Ladies College, when my daughter attended, was barely, if any better than the educational level of the free, State run schools on the island. Their entrance requirements are non-existent and anyone willing to PAY apparently gets in. It was, in my opinion £15,000 a year down the drain.
Elizabeth College is even worse. Infested with "modern", Leftist ideology, your boy (or now girl) will get an education that is not as good as some of the schools in guernsey that are free.... Forest School, for example.
A MUCH better option is Beaucamp School. It costs the same as Ladies and Elizabeth, but has a VASTLY higher level of education. Yes, it's notionally a Catholic school, but religion is in no way forced upon children or a significant segment of the course matter. It's all about good education at Beaucamp....and your kids will emerge very considerably better educated than from either of the other two under discussion.