Stats give a neutral view point.And i can tell you i have watched enough cricket.
They have also played similar number of matches since
1 Jan 2013
Yadav 49 wickets @ 25.8 in 31 matches
Riaz 37 wickets @ 35 in 29 matches
See the huge difference in performance in last 2 years when they have played almost similar number of matches.Yadav is far ahead of Riaz
Now lets see what they have done since
1 Jan 2014
Yadav 37 wickets @ 21.5 in 20 matches
Riaz 29 wickets @ 26.3 in 15 matches
Again Yadav is comfortably ahead
Now coming to their
career performances
Yadav 67 wickets @ 31.44 in 48 matches
Riaz 77 wickets @ 30.2 in 54 matches
Here Riaz is ahead by a small margin.
Considering neither one has a very long career and both of them have played more than 50% of their matches in last 2 years Yadav is ahead of Riaz.
I guess you have no idea about Yadav.Yadav have been out of the team with a back stress fracture and had to modify his action and has been out of the team for a long time and then been in and out of the team while India preferred the likes of Mohit Sharma/Vinay Kumar and co.
So this consistent run argument doesnt stick as both have played almost similar number of matches since 1 jan 2013.
In Limited overs cricket Kohli is considered slightly better because Kohli has played some very good innings chasing and also because Kohli is miles ahead of the batsman Amla is in T20s.Amla comfortably beats Kohli in Test matches.Overall Amla is a better bat.