Local temporary table VS derived table type

Hi all,

As i saw from tutorials or posts developers are writing their codes like

ET_VAL = Select .........

i didnt' get why people are using like that ?

I just made a performance test using on my Procedure

ET_VAL = Select * from table 

vs

create local temporary table #et_VAl like ZXXX ;
select * from table into #et_val.

Procedure has 500 lines of codes with more than 30 selects.

If i use temporary tables, code runs faster comparing to derived table type. (here i assume, system trying to create structur dynamically )

But advantage of derived table type (i dont know if the "derived" terminology is correct) is no need to use drop statements and on system resources perspective may be more efficient.