We understand your question.
Here is the problem.
One machine digs for gold.
The other digs for copper silver tin.
So what you want to know is. What price of what coin will hold up the best.
Today the s9 would be a loser.
In a week the s9 would be a loser.
But in two months if btc jumps to 900 and the alt coins drop a bit
The s9 is a winner.
I would advise you to understand that all gear profit is based on multiple factors. Alt coin and or btc
Guessing what to go for can hurt you big time.
I mine btc with s9 and I mine eth with gpus