The first one definitely has a reflection in it, as there's a slight ripple. Sometimes I leave a little reflection in the measurement. But you're right that those both are ugly responses. Can't recall seeing those before. Bills post also acknowledges those look a little off.
The reality is though, the SEOS looks a whole lot better than that on all other measurements I've seen. The DNA-350 has some notches (3) that are quite slight above about 5khz I believe. Otherwise all the other CDs I've seen measured on it are really smooth, off axis too.
What is most important Ash, is the final result in the design. It's good to pick a design with detailed measurements that show even off axis behaviors, good on axis FR, a wide vertical lobe, etc. you won't get good results if the waveguide can't do it. Like a lot of round waveguides. Both the SEOS and the Pi (H290 or something, can't recall) are good at doing this. It's been noted that the Pi has slightly narrower directivity, like 10 degrees. Depending on the application, one may be preferred, but generally negligible. For me, a little wider from the SEOS is preferred cause I have 8' wide seating and a 10' viewing distance. I also like to cross low.
They're honestly very similar and are state of the art IMO. Well, maybe a SEOS 24 is state of the art! We'll find out soon