Ki Aikido is so soft in nature, many Aikido practitioners dismiss this style all together. I personally have never practiced Aikikai Aikido, so to speculate would not be accurate or fair. It looks real cool, and more harder in nature. The question is, can the extreame soft style of KI Aikido be just as effective in the street as Aikikai Aikido?
Shin Shin Toitsu / the Ki Society definitely don't have the monopoly on softness! My experience of the Yamaguchi line (Yamaguchi himself, and also Endo and Yamashima) has shown me what can happen if you let go of muscular effort and replace it with something else. I gather some Aikikai practitioners are sceptical about these teachers, but I for one have no doubts at all...