When you get tired of it, what are you going to do?
In my own opinion, if energy is cheaper or friendly in your location, you can give GPU a trial as it offers more benefits such as no noise, algorithm switching, can be customized and you can also resale when the need arises.
actually if power is cheap you should do some gpu and some asic
if power is cheap (or free) it's better to choice S9
10 x S9 = about $2000 = 140Tx 13 kW/h
2 x S17Pro = about $5000 or more = 125Tx 6 kW/h
and we have ~3000 dollars to pay for cheap electricity
Also got to remember that you have huge amps to contend with for the 10x S9 option.
13kW is minimum 55A
And S9 is closer to 1500W per unit than 1300W, driving that amperage up to over 60A which potentially puts you in need of some professional electrician and modifications to existing circuits.
The S17 option you mention, which is more likely to draw around 2200W per unit depending on the model you go for, would leave you needing less than 20A. Even most homes could handle that as an addition to your regular domestic circuit.