In the past I've seen use of something such as
SELECT ISNULL(NULLIF(Field1, ''), 'NewValue')
to tersely get a fallback value.
However, since the advent of CASE in TSQL, we've favored something more like
SELECT CASE Field1 WHEN '' THEN 'NewValue' ELSE Field1 END
Is one going to perform better than the other? What other reasons would there be to choose one over the other?