'SELECT TOP' performance question
SQL Server builds different execution plans for TOP 100, using a different sort algorithm. Sometimes it's faster, sometimes it's slower.

For simpler examples of it, read How Much Can One Row Change A Query Plan? Part 1 and Part 2.

For in-depth technical details, plus an example of where the TOP 100 algorithm is actually slower, read Paul White's Sorting, Row Goals, and the TOP 100 Problem.

The bottom line: in your case, if you know that no rows will be returned, well...don't run the query, eh? The fastest query is the one you never make. However, if you need to do an existence check, just do IF EXISTS(stick query here), and then SQL Server will do an even different execution plan.