Which cpu is best

Solution
There is only a ~$50 difference between the R5-1400 and R5-1600, which makes it difficult to recommend AMD's lower-end R5 chips.

Between an i3 and the R5-1400 though, the R5 still has much better bang-per-buck and processing power headroom for future software.
It really depents what you are looking for, all three are similar in a way. You could find cheap good 170 motherboards that can cover the difference of 6 to 7% performance over the z270 boards. If you are a gamer go for intel or if you need more cores for video editing or other demanding tasks go for ryzen
 
There is only a ~$50 difference between the R5-1400 and R5-1600, which makes it difficult to recommend AMD's lower-end R5 chips.

Between an i3 and the R5-1400 though, the R5 still has much better bang-per-buck and processing power headroom for future software.
 
Solution