I have visited the yoshinkan schools in my area, and it is a world of difference to my aikikai/ki/seidokan blend. It is definitely a hard style that seems (unless I'm mistaken) to rely on some amount of strength to break ukes balance. In talking to sempai, they don't use energy the way other styles do and to me it seemed quite stiff and mechanical. It is, I have no doubt, very effective in a practical sense. (Or the Tokyo police wouldn't use it
It seems that what could be termed "ki" development is reserved for dan ranks that have mastered the kihon waza. I have heard Inoue Dojo-cho has incredible energy. But, I guess what I found to be the most interesting is that the yoshinkan probably has the best use of angles and the techniques are very pure to the Founder's original pre-war budo. If someone says that yonkyo doesn't work, have a good yoshinkan practicioner apply it. Their theory of a "bolt lock" makes it a very, very practical and effective technique.
Just my humble opinions and observations