As Davey says, why not try some benchmarking and find out.

It depends on a number of factors, but generally the implicit cursor will be faster.

'Select into' used to be almost frowned upon, maybe that is where the developer is coming from.

It's much easier to interpret:

select field1 into variable1 from table1;


than

cursor cursor1 is
select field1
from table1;

begin

open cursor1;
fetch cursor1
into variable1;
close cursor1;


I know which one I'd rather read.