There's no way Bono could have joined the Virgin Prunes first. They didn't exist until Dik Evans left U2 (or more correctly The Hype) to start a band with Gavin, Guggi et al. And U2/TheHype existed first because of Larry's initiative, not Bono's. Anyway, Bono never had much interest in doing the kind of in-your-face performance art those guys wanted to do. The criteria for being in one band or the other wouldn't have been which one has your closest friends; it was which approach to performance are you most interested in.