I think Artist Point is more beautiful during daylight. It is very light with high ceilings. For Jiko I think it looks better if it is dark outside. There is not much of a view and they do intersting things with their lighting, so I think the effect is better later in the day.
For checking the last available time I would try out the new online ADR system on the Website and see what is available. I am pretty sure we had a 9 pm reservation once for Jiko.