Economy or PE to UC with miles

I am just too lazy to do it and I am sure it someone has already worked this out.
Which is better value, buying an econaomy or premium ticket if you want to use miles to upgrade to UC?
I travel to the west coast, LA or SFO, quite often and would ideally do PE during the day and UC at night.
Which is better value, buying an econaomy or premium ticket if you want to use miles to upgrade to UC?
I travel to the west coast, LA or SFO, quite often and would ideally do PE during the day and UC at night.