Has anyone here have experience with TaxJar - NetSuite integration? How is Taxjar different with Avalara?

Yes we replaced Avalara with Taxjar a while back. TaxJar has a REST API.

So it's not a SuiteApp right you need to integrate the data though Rest API? Any challenges and what were the advantages and disadvantage of Using TaxJar versus Avalara?

When we implemented, they didn’t have a SuiteApp but I believe they were heading in that direction. The main reason for replacing Avalara was cost. The TaxJar approach, while quite flexible, means that you would need to code to send data to TaxJar API to return the tax calculations.