OK. I would analyze your two options this way:

Since UR points can be converted to Avios on a 1:1 basis (except when there is the occasional transfer bonus), your options look like this:

33,000 Avios + $257 = 33,000 Avios (converted from UR points) + 27,552 UR points.

Subtracting 33,000 Avios from both sides of the equation, you get:

$257 = 27,552 UR points
That's less than 1.0 cent in value per Avios. That's pretty poor value, so I would opt for the 33,000 Avios + $257.

What's the cash cost of the three tickets?