I'm very far from any sort of status for any program although I have a healthy # of miles in either. When I fly a one world airline, I credit my miles to CX, and when I fly Star Alliance, I credit the miles to UA.

So basically, to credit 5000 miles into one world, its a $569 fare, and to credit to star alliance, its $733.

Based on brief calculation of air fare I have:

TPE to BKK 1 Way Economy:
UA: 15000 + $85
CX: 20000 + $78

LAX to HKG 1 way economy:
UA: 32500 + $80
CX: 40000 + $143

SPG points to CX, its 1:1 conversion.
SPG points to UA, its 2:1 conversion.

So its fairly clear that star alliance points are not worth as much as one world, but one world aircraft tend to be newer, J/F seats are generally more modern/higher quality.

I'm just not too sure what average value is placed on a mile to see if its worth crediting one or another... thoughts?