Yes I agree. Both queries are executing in under 1 sec. so time can't be a measurement factor, may be in a very very big query we can see some difference.

I am finding same issue with DISTINCT and UNION where execution plan, IO and time is exactly identical for these three scenarios (Though query 2 gives different results):

(1)

select DISTINCT .....

UNION

select DISTINCT .....

(2)

select DISTINCT .....

UNION ALL

select DISTINCT .....

(3)

select .....

UNION

select .....