Is this the right choice?
The 2017 model has a newer generation processor - but also a lower wattage processor than the 2015. Odds are, it will still be measurably faster than the 2015, but don't expect a dramatic difference.
Why would you be tempted to pay a bit extra for older tech and slightly lower performance? Well:
1: The keyboard on the 2016/2017 model is a bit love it/hate it. If possible, get to a store, try the keyboard on a 2017 MacBook Pro and see if you like it (they won't have a 2015 MBP to compere it with, but the 2015 keyboard is more like the one on the MacBook Air, which they probably will have).
2: Do you need to connect to a lot of USB peripherals, Thunderbolt 1/2 devices, Mini DisplayPort displays or adapters, or HDMI displays, or use SD cards, or have existing MagSafe chargers, Thunderbolt Displays or LED Cinema Displays (with MagSafe chargers built in)? The input/output port provision on the 2017 non-touchbar MBP - two USB-C/Thunderbolt 3 ports and nothing else - is pitiful unless you're going to take advantage of Thunderbolt 3 peripherals and docks. If you live a mostly wireless life, it may be an issue, but if you need to connect to a lot of existing stuff then you could end up spending hundreds on cables, docks and adapters.
...if those issues affect you, then getting the "technically inferior" 2015 model might be a more practical solution. If you'd asked 6-10 months ago, I'd definitely have gone for the 2015... but time is passing and the 2015 processors aren't getting any younger.
Still, if you went 2015, I'd shop around to see if you could get a 2015 for
less than the 2017.
