I refer you to Tom's Hardware's own CPU Comparison Chart (June 2015):
http://www.tomshardware.co.uk/gaming-cpu-review-overclock,review-32901-2.html
The AMD Quad-Core Athlon X4 860K got their best buy for ~£75 whereas the i3-4170 got their best buy for under £100.
Ultimately:
Speed: Identical: 3.7GHz
Cores: AMD: 4 Intel: 2 with 4 threads
Cache: AMD: 4x 96KB + 4x 16KB, 2x 2MB // Intel: 2x 64KB, 2x 256KB, 3MB
Integrated Graphics: AMD: N/A // Intel: HD Graphics 4400 (350MHz, 1.15GHz Turbo)
Memory Support:
AMD: DDR3-2133, dual-channel // Intel: DDR3-1333/1600, dual-channel, up to 32GB
TDP: AMD: 95W // Intel: 54W
Thus, it's hard to say which is better, as I don't know if you need integrated graphics. One chip has them, the other doesn't. Tom's Hardware recommends them both in different price ranges.
On CPU Boss:
http://cpuboss.com/cpus/Intel-Core-i3-4170-vs-AMD-Athlon-X4-860K
The i3 has a better PassMark (Single Core) score.
AMD has better overclocking.
There's also a discrepancy between cpuboss and Tom's Hardware as it says on Tom's Hardware that the AMD is only a dual core processor with 4 threads. Most other sources state it is a quad core processor. (Thus I updated my summary above).
Ultimately (PERSONAL CHOICE), I'd go for the AMD if I was using a discrete graphics card for the overclocking ability but go with the Intel if I needed integrated graphics.
JT