Personally I would go get the boy fixed as Elena said earlier its a much less intrusive procedure for males. If you plan on keeping them indoors I wouldnt get the female fixed either but thats just my personal view.

Im all for neutering in the right circumstances, I have a female cat who is neutered because shes an outdoor cat but I wont get my boy done as I know he will never be let outside and therefore feel its uneccesary.