All speculation because I don't have summer homes in any of those guys' heads, but just from a draft/ $ standpoint:
- I think McRoberts and Singler probably made bad decisions in returning - McBob went from a lottery pick to 2nd round, and Singler went from late 1st to 2nd. One can argue, with the benefit of hindsight, that Jay Williams would've been wise to get two years of NBA ball under his belt before suffering a career-ending injury (though who knows if he would've been in the same place if he'd made different decisions).
- Battier, Redick, and Shelden Williams all benefited greatly from returning - all dramatically improved draft prospects in their senior seasons. Nolan Smith did as well, though I'm not sure leaving after his jr. season was all that realistic an option.
None of that factors in the intangible value of another year at college and such, but that's such an individual thing that I think it's just totally unfair to try and place oneself in another's shoes.