If you need everything that starts with As, then you can't use an equality, the LIKE is probably the best.
Btw, don't look at the subtree cost. Costs are pretty much meaningless values, look at the execution statistics instead, the duration, the CPU, the reads. Those tell you how a query is behaving.
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