AJ - What are the main differences between Daito-ryu and aikido?
I don't think there is any difference. In Daito-ryu, too, practice begins and ends with courtesy (rei). And its final goal is the spirit of love and harmony.
AJ - How about technically?
I do not think that there is much difference technically, either. However, we have what we call ikkajo, which consists of thirty different techniques, ten of which are seated, five hanza handachi, ten standing techniques (tachiai) and five rear-attack techniques (ushirodori). Each of these thirty techniques has its own name. In Daito-ryu, the first technique you learn is called ippondori, a difficult technique where you receive, barehanded, the frontal attack of your opponent.
In the traditional martial arts, a secret technique is usually taught at the very beginning. In Daito-ryu, too, we teach a difficult technique first. This ippondori, I believe, has become ikkyo in aikido and also is related to techniques like shomenuchi ikkyo, katatedori ikkyo, ryotedori ikkyo, and so on. Ikkajo consists of t hirty techniques, but only the ippondori technique became ikkyo in aikido. There are twenty-nine other techniques such as gyaku udedori, kurumadaoshi, koshiguruma, and so on. Nikajo also has thirty techniques and only one of them is called nikyo in aikido. And the case is the same for sankyo. Yonkajo includes fifteen techniques and one of them is called yonkyo in aikido. Gokajo has thirteen techniques and one of them is gokyo in aikido. It includes tasudori (techniques against group attacks), tachidori (techniques against a sword), jodori, kasadori, emonodori (techniques against various weapons) and so on, all of which were practiced in the old days.
So we have 118 different techniques, classified as the ikkyo through gokyo series in Daito-ryu. These make up the hiden mokuroku and only five of those techniques were included in aikido. I would like this to be clear, to avoid any misunderstanding.
The difference between aikido and Daito-ryu in the eyes of the general public is that in techniques of Daito-ryu you must break the balance of your opponent the instant you touch him. This is because there is aiki in the technique, which we use to break the balance of the opponent. This is a major characteristic of Daito-ryu. Another characteristic is its use of atemi. This atemi is also a part of aiki in Daito-ryu. Although it is often said that Daito-ryu looks unrefined or is lacking in magnificence, Daito-ryu also has a component called aiki no jutsu (fifty-three techniques) and they are truly wonderful. The aiki no jutsu techniques come after the 118 hiden mokuroku, and they are followed by the hiden ogi, the hiogi, the kaishaku soden, and finally the kaiden techniques.