So, I have finally figured out that in my case, the problem was not iTunes, but iPhoto.
My whole system was going unresponsive whenever I plugged my iPhone 5 in. I assumed it was iTunes syncing, but it was actually iPhoto attempting to launch and sync photos. It was getting stuck at such a low level that the icon never got a chance to appear in the Dock nor did it show up in Activity Monitor.
I figured it out after attempting to launch iPhoto manually for the first time since my Mavericks and iPhoto upgrades. Sometime around then, my photo library got corrupted. After iPhoto completely hung my system and I was abel to Force Quit it, I was able to spot some messages in Console. Several messages like below, led me to do the 'mdutil' search and turned up "~/Photos/iPhoto Library/iPod Photo Cache" folder as a problem. Moved it aside, and iPhoto was able to launch again.
mdworker(74813) deny file-read-data /Users/spencer/Pictures/iPhoto Library/Contents/PkgInfo (pre-plugin fstype:hfs fsflag:480D000 flags:250000005E diag:0 isXCode:0 uti:public.folder plugin:internalPlainTextImporter - find suspect file using: sudo mdutil -t 805196)