I've recently posted on just this subject in "Is buying maiden gilts a risk". We always started them off with AI as we had Saddlebacks and Tamworths. As I wanted to breed pedigree for both, it would have meant organising transport/loans of two separate boars, complications with housing them and standstill periods if they overlapped. I found AI incredibly straightforward and successful, as long as you are very well prepared knowing exactly when your gilts are ready for insemination, as there is no boar to tell you.