All of them I mcguess.
I haven't read RoaDK in a while but I always thought that Krondor fell in a short period - hardly even a siege. It seemed to take very little time even if there was a fair bit of description. I always kind of considered a seige lasting at least a couple of days. The second seige that begins in SoaBC is better in this regard than the first one mentioned - to my way of thinking anyways.
Olasko is in my least favourite Feist series so I'm probably a tad biased on that front.
Sethanon seemed to get very little coverage' in terms of the action of the seige, at least thats what I remember, so.....
Darkmoor was important and more drawn out but seemed to be mainly a side-story whilst I felt the key plot machinations were taking place elsewhere most of the time, with Pug etc.
Crydee gets a fair descript and is important, to me at least, and in the wider picture of Magiacian as well. This is the seige that comes closest to Armengar in my opinion.
My tuppence worth!