"What is more effective for Self-defense, Aikido or the Parent Art of Aikido, Daito-Ryu Aikijutsu?"
We do have some of the words and thoughts of Ueshiba Sensei, however, and I have obtained them from an online resource and I believe I can take a few excerpts from this 1957 Interview and this should cast some light on the matter.
Ueshiba Sensei was asked several questions, I think from the answers, just looking at them as a commentary, you can see what I mean...
"In my opinion, it [Aikido] can be said to be the true martial art. The reason for this is that it is a martial art based on universal truth. This universe is composed of many different parts, and yet the universe as a whole is united as a family and symbolizes the ultimate state of peace. Holding such a view of the universe, Aikido cannot be anything but a martial art of love. It cannot be a martial art of violence.
...Since I taught martial arts to be used for the purpose of killing others to soldiers during the War, I became deeply troubled after the conflict ended.
...In Aikido, there is absolutely no attack. To attack means that the spirit has already lost. We adhere to the principle of absolute non-resistance, that is to say, we do not oppose the attacker."