Ultrasonic
Addicted to Fun and Learning
The SU-8 also has a built in power supply so for those who don't want to power a D50 via USB to a PC there is the added benefit of not needing to buy one (or potentially stressing about the quality of whatever is used).I am relatively new to the audio world so look for more opinions, but from the reviews it seems that they both are excellent value and similar in performance. I think you should look at their features and what you need or might need in the future, the SU8 has balanced outputs in addition to RCA out and a remote control while the D50 only supports RCA and no remote control.
Comparing the unbalanced SU-8 results to the D50 there is very little in it as you say. The SU-8 SINAD is a tiny bit better but the D50's linearity is better. Although I think in practice this difference is pretty moot.