I'm trying to keep my entire library in the scenery.cfg format. Over the past year, many developers have been transitioning to xml. While I don't fully understand the technical goings on in P3d when xml based scenery entries are used, I can tell you that when I did have all my scenery added in this way, load times were exponentially longer, I was getting constant stutters / long frames and I was experiencing ctd's fairly regularly.
In attempting to solve my ctd issues, I was suggested by another developer to move all my scenery back to the scenery.cfg method. Once I did, my load times are much faster and I can't recall the last time I had a ctd (well, it was before I made this change). I have no long frames at long - frankly, this is the best performance I've had in p3d I think ever.
I'm not suggesting that there wasn't some other underlying issue that was causing my problems, but it sure seems that moving back to the direct library entry has solved a lot of that for me.
Normally, this change can be made fairly simply, by removing the folder placed in the p3d addons folder, and then directly adding the scenery within the library manager. For some reason, when I did this with the new KORD, I think the dynamic lighting was not on at the airport. For now, I just reinstalled and now I have it as the only xml scenery in my rig. So far I'm not experiencing any problems, but I think the issue I was having was from the many scenery and airports I had, all being added by xml, and collectively causing problems.