Really, it comes down to the condition of the chain. I often do not change the chain or front sprocket (Steel) when the rear is worn. I can usually go 2 for 1 and get SIMILAR life from the second rear sprocket.
That said, if you can get a steel rear...do so. They only weigh grams more than an aluminum one and will double the life span. In fact, I usualy wear out a chain before the sprockets when I have steel. Any new chain gets new sprockets.
Of course you look like a N00b with a steel rear sprocket, but then you can take satisfaction in your intellegence and look at the kool kids for what they are; silly, BNG sporting, bling touting posers.
(If you don't know what BNG is...you might be a N00b.)