That's a tough question, not on a technical level but on the subjective one. The reason is that I used those KSN1038's for soooo long - 25 years - and they've been a part of the one π and two π speakers since the 70s. That's a long time.The KSN1038 is a good little part for this speaker. It sounds good and doesn't cost much. It's tough as nails, you can't break it. And it is an attractive part too.
The Vifa soft dome tweeter has flatter response and sounds very, very nice. It is unquestionably a better part, but it costs 4x as much too. The crossover region is smoother because the soft dome tweeter is capable of lower frequencies and also because it simply has a smoother response curve.
All-in-all, I think they're both very good. I have both speakers, and I like them both. The version with the soft dome tweter is a little more refined sounding, but the one with the KSN1038 is a classic. It's hard to say which I prefer, but I guess it's a mute point since the KSN1038 option is gone.