Scoring not alone makes them best batsmen,their techniques and range of shots.
Okay lets take Sehwag and Dravid as an example,Sehwag scores more runs than dravid on most of the matches but based on techniques Dravid is most stronger than Sehwag so now who you will say as best batsmen?
You are comparing an attacking batsman and a defensive batsman, Virender Sehwag had a solid defense and good balance and his plus point was his hand eye coordination and he scored runs as long as his hand eye coordination was crisp, Virender Sehwag changed how openers played Test cricket as earlier we used to have batsman that could defend all the time to reduce the shine of the ball and Virender Sehwag came in and changed everything. So both are great players in their own right.
You can also compare him with Sachin, he is the number one batsman in the world till now. He did not have a technique like Dravid but still was a match-winner most of the time. I never heard Dravid being called as a match-winner but a wall to hold middle order. Technique do not work when you play cricket nowadays. It is always the presence of mind and choosing the write short at the write time.
You really cannot compare techniques like that, Sachin had the best balance and the best technique and he had the best defense and offense and if not he could not perform well for 20 years around the globe and when they were playing all the countries had world class bowlers who could challenge any batsman and yet they were able to score runs against any class bowlers and without proper technique and shot selection you will not survive this long.