1.Merchadise profit may be related to PR lv, but the amount increase per week is too little compare to the salary increase
2. PR incrase attendence, especailly when u won the previous game. Think of it this way, if u keep winning, u attendence will increase a certain amount, the higher lv PR only make the increase goes faster. So if u have, many extra seats and keep winning, it is wise to go a better PR.
3. better PR = better fan survey as manual said
4. better PR allow u charge more, because the demand of ticket seems to increase
5. lv2 PR above have specailty that may be worth a few point in a home game
my recommendation
always buy specality
lv 2 for all people
lv3 only if u are winning and ur stadium is not full
lv4 only if u can raise the ticket prize and charge the people back
lv5+? need a very large stadium(over 300K attendence income) to make it cost effective