Execution plan shows you how the query runs, not its performance characteristics.
But execution plan shows that 2nd query is performing 80% better then 1st query.
No it doesn't. It shows that the estimated cost of one is 80% lower than the estimated cost of the other. That's it.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability