nijo castle or imperial castle tour?

which one is better?
nijo castle has the flexibility, the imperial castle already booked, but the time is not flexible for me, but i dont mind. But which one is better?
Has anyone do the tour?is it interesting?

I've visited both. I personally prefer Nijō as it's possible to enter the actual palace building and admire its richly decorated interiors up close, whereas at the Imperial Palace, the official tour only takes you past the buildings (you can't actually go inside them).

But if you have the time, by all means visit both.

Pictures from my visits here:

Imperial Palace
Outside the walls (accessible to anyone) - https://withinstrikingdistance.wordpress.com/2013/07/14/field-report-k...
Inside the walls (only accessible on an official tour) - https://animeaffairs.wordpress.com/2009/08/30/japan-2009-highlights-ky... (note that the post is split up into pages)

Nijō Castle
https://withinstrikingdistance.wordpress.com/2013/07/04/field-report-k... (note that you can enter the Ninomaru Palace, but photographs are strictly forbidden inside so I have no pictures of the beautiful interiors)

Cheers.

I would second Diego.
Go for Nijo Castle, especially if you have to choose between the two. I found Imperial Palace a wee bit boring.

If this is your first time and you have to select one of them, I think the imperial castle tour is more worth: It is one of very rare tours with English guide and free-of-charge.

I have done both and can add to what others have said. There is no bad choice in this, both are well worth the visit. Personally if I HAD to choose one the I would do the castle.

ok then i will cancel my reservation with imperial palaca and do the nijo castle. how long the time we need to explore the castle?
i will arrive at kyoto at 12 noon, then take a lunch, go to nijo, kinkakuji, then arashiyama (tenryuji , bamboo forest, bridge) then back to gion to have dinner, is is doable?
any another interesting site at arashiyama?