I agree on the overall "look," but the SS86 van mode isn't bad by any means, and looks the part well enough.
The problem with the ER van is that it had too many issues that just didn't work. The should blocks cutting off the windows, the feet just sticking out, the Cybertronian wheels. I actually like the shield roof, that was the right kind of Diaclone throwback I can get behind. The rest though.... yeesh.
I tried though. I got the set to replace the feet with feet that transformed into a real van back, and while they looked the part they utterly fail to clip together in van mode. So even if the feet no longer stand out like they did... they still don't look good.
And after that swing and miss I just decided to stop trying to make such a flawed mould work and go with the SS86 one. My major issue with it- the flat Sunbow deco- was easily solved with the ToyHax toy-accurate set. So the cost of one set of stickers vs a bunch of third party add-on kits that may not work?
SS86 won.