I'm glad to see this thread is still active. In the 4 or 5 years since I began switching to macs I've looked for an osx app that does precisely what you asked for, murrayE ;-) I bought pathfinder, transmit, chronosync--they're all fine for their particular uses, but don't exactly do the things you ask for. I tried forklift, but that didn't fill the bill for me.
I was pleased to learn about kdiff3 in this thread. I downloaded it & will give it a try!
Beyond compare looks like a great program (haven't used it in windows though) and I have followed its developers' efforts to get that ported to osx--I'd surely buy it if that happens.
But for hundreds of Gb of photo libraries and mathematical & statistical modeling and analysis work, I need something which I can absolutely, positively trust and that is transparent & easy to use. Just haven't found that on osx yet.
For now I continue to rely on win apps I've used over 15 years. I keep Total Commander (TC)
(ghisler dot com) running in a win7 parallels vm (actually in a coherence window on my osx desktop). I use the internal file & directory compare/sync tools in TC some of the time. Most of the time I use Compare It! and Sync It! from (grigsoft dot com) for file & directory compare/sync. I put the source & destination directories in Total Commander's 2 file manager panes and then have an icon on TC's "button bar" which launches Sync It! as a subprogram. TC's file & directory compare/sync tools are great, but the ones from Grigsoft offer much richer customization options for the file or directory operations (and they have a pleasing and functional UIs). Plus you can save custom setups with different parameter & option sets for different types of jobs you might want to do with the grigsoft tools.
Parallels 8 runs win apps rock solidly for me. Programs and subprograms just open up right on the desktop (in coherence mode).
I haven't figured out why similar tools didn't seem to develop for OSX. There are several fine OSX sync programs, but I have had trouble getting them to do what I want: Chronosync is fine for backing up a drive, but I've found it for ,say, syncing 1 main folder with hundreds of populated subfolders from a source to a target drive--I can do it, but I've got to be crazy careful or I'll end up duplicating the folders & files inside of one of the target folders or some similar error--instead of just updating the target with changes in the source. I like Transmit, but while I can get it to do precisely the type of directory sync from my local source drive to e.g. a remote web server, I cannot get it to do the same thing onto, say, my local file server.
I'm happy to use unix command line apps and have used them a lot over the years. But I don't find some script I've written with diff or other utilities as transparent or trustworthy as a GUI which gives me that visual confirmation I like. Wouldn't have rambled on so long except that just now I'm almost done with a Sync It! run checking over 91,000 files and hundreds of Gb from some photo libraries and I can see each file's status before and after. And for some reason a new USB3 destination drive is dismounting on its own which could be catastrophic. Yet Sync It! handles this pretty gracefully, notifying me of files that didn't get copied and letting me rescan and resume.
I would prefer a native OSX app as doing OSX file management with a win7 vm is a bit scary for a relative osx newbie. But fortunately apps I use like lightroom & photoshop and even mathematical modeling stuff like R and Rstudio, etc. don't seem to mind. The differing permission systems and hidden files like .DS_Store are a bit of a worry, but I haven't clobbered anything in the past 5 years. (Early on, I did have to learn how to reset file permissions with terminal commands ;-) but I don't have to futz with such things much recently.)