Depends on what he plans on doing with it.
Quickbooks is King.
Peachtree is playing catch up (well, not really).
It has changed hands 3 time in 4 years.
ADP owned it and sold it off to a company (Sage) that bought it
for the sole purpose of selling there own (MAS90) software to the
install base of Peachtree customers.
Quickbooks is more intuitive and has a easier learning curve.