INSERT Performance

[StoneDeCroze]

Hi All,

I have two tables and I want to insert data from them into a third table.
Question:
Am I better to write two inserts statements e.g.

INSERT INTO table3 (field1, field2) SELECT field1, field2 FROM table1

and

INSERT INTO table3 (field1, field2) SELECT field1, field2 FROM table2

OR one insert statement

INSERT INTO table3 (field1, field2)
SELECT field1, field2 FROM table1
UNION ALL
SELECT field1, field2 FROM table2

Are two inserts better or worse than one insert and a UNION ALL.

Cheers
Peter