Do it, if you feel confortable about buying GPU's instead of S9 or just antminers, then do it.

You should know that the demand for both devices is HUGE, it is going to be difficult to get a bunch of GPU's worth of the same value of 10 S9.

And yes, altcoins are more profitable, you should know that everytime that you want to move your bitcoins you need to pay $40 worth of fees (aproximately)

If you have 10 s9, this could be aproximately 7 hours of mining without counting how much money do you need to pay for the electricity.

And if you mine altcoins, it will cost you no more than one dollar per movement.