whether the computed field affect the performance and  speed of the table?

simple example :
table x
value1 integer
value2 integer
total computed(value1+value2)

table y
value1 integer
value2 integer

query1

> select * from x
> select total from x

query2

> select * from y
> select value1+value2 as total from y

Which is better performance and speed? table x or table y ?

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