In both X0 and XY methods of sex determination,

In both X0 and XY methods of sex determination, male is heterogametic. In X0 method, male produces two types of sperms. Half of them have X chromosome while the other half do not carry any allosome. In XY method also male produces two types of sperms. Half of them have X chromosome while the other half carry Y chromosome. 

Male and female have equal number of chromosomes in XY method because both male and female have two allosomes. Male and female have unequal number of chromosomes in X0 method because male has only one allosome while female has two allosomes.