Ok, i think that if we are talking about grammar tasks, the answer is Would becuase is more useful use it with the clause "If" for the conditional sentences....be happy... = )
Would usually, refers to future tenses.
Should refers to giving advice or orders.
In conclusion, would and should are used in diferent context
Expecting your comments
I am suprised that should didn't get more hits.'I should like' would usuallly be formal
'would' blows the doors off 'should'
the question is asking which is more formal, not which is more common......i think "should"
'I would be
is more formal and correct
In fact, we had better keep on writing after if. In such a condition, it seems short and insufficient to understand for some learners.
We can use the modal SHOULD to correct the mistakes or misdeeds.
A: I is a student.
B: It is a wrong sentence. You should write I am a student.