The diffracne between Sales Comparison Approach and Cost appro

[Tomer Kamil]

I recently had an appraisal on a potential home i'm seeking to buy.

What is the diffracne between Sales Comparison Approach and Cost approach?

When I buy a proporty should I pay for it acoording to the Sales Comparison or Approach and Cost approach? 
The Sales Comparison was $137,500 and the Cost approach was $169,672 acoording to the report.

Thanks