An interesting thread. A few thoughts.
1. I think that what Mr Seagal does in his films should not constitute a norm for dojo practice. The situations are completely different. Of course, in a demonstration it makes tori feel good to have uke flying across the tatami, but demonstrations, like films, are not the norm for aikido practice. (I think demonstrations, like films, deserve a separate thread.)
2. I usually teach kotegaeshi as a katame waza, with an arm pin at the end (best done from a chudan tsuki). As, for example, for tanto/tachi dori. Here, there should be no question of uke having a choice whether to take a forward breakfall or do an ushiro-ukemi. If uke has such a choice, this indicates a major lack of control on the part of tori, in my opinion.
3. Yamaguchi Sensei once told me that executing kotegaeshi was like rolling up a carpet. Carpets are not usually rolled at waist height.
4. I suggest two training exercises for good kotegaeshi:
(1) A game. Tori should throw hard, but always aim to apply an arm pin. Uke should try to take ukemi and stand upright before tori can apply the pin. This exercise is very good for sharpening both tori's and uke's technique.
(2) Kaeshi-waza from kotegaeshi to 3-kyo, or reverse kotegaeshi (see M. Saito, "Traditional Aikido" Vol. 4).
Finally, most of the posts in this thread have focused on the wrist. But this focus obscures several crucial points of aikido techniques. The correct order should be: (1) Move out of the line of attack; (2) Unbalance the opponent; (3) throw the opponent.
The question of what ukemi is best for uke to execute misses all of these points.
Best regards to all,