Hi Kevin, there are many other items which will effect sound quality - noise floor / grounding issues / interference etc. The DAC chip itself may also be adversely effected by a bad board layout.
You may also want to consider how you want to go about measuring the differences. By ear or by something like an Audio Precision analyser at £15k 
You may also want to consider various use cases? Built in volume control? Is full 2vrms (line level) output needed? Frequency and bit depth support? CPU overhead at different frequencies when using USB.
As you say - a plethora of variables / minefield.
Burr Brown was purchased by TI in 2003 IIRC - don’t think the Wolfson part is Burr Brown derived as the WM5102 is a much more feature rich beast (note I didn’t say better) than the TI PCM5102.
If you don’t have an IQaudio Pi-DAC already drop me a PM and I’ll have one sent to you.
Very best regards,
Gordon