Which is quicker COALESCE OR ISNULL?

Question

I understand the difference between these functions but my question is when checking for a single null value would ISNULL be any quicker than using COALESCE?

e.g

Answer 1

I just ran a test on my own db. About 700k rows.

SELECT COUNT(*) FROM table WHERE COALESCE(field_1,field_2,field_3,field_4) IS NOT NULL

Result of 12106 obtained in 56 seconds.

SELECT COUNT(*) FROM table WHERE field_1 IS NOT NULL OR field_2 IS NOT NULL OR field_3 IS NOT NULL OR field_4 IS NOT NULL

Result of 12106 obtained in 0.00 seconds.