I like Conception, but it's definitely Kamelot. I don't feel Conception is "PURE BRILLIANCE!" like so many music reviewers seem to. Ten bucks says that if Conception were still around, they would not get half of the praise that they do for stopping after a few albums.
And IMO, Siege Perilous and The Fourth Legacy could have been made by any other power-prog band out there. The thing I like about Kamelot is that they have come to embrace the power of groove and riffs that do not center solely around thrash and double-bass.
The Black Halo is golden to me. Ghost Opera is pretty sweet. Karma is badass in many moments.
The further you delve into Kamelot's back catalog, I think, the more unfocused and unimpressive the music becomes.