There is one major difference about the Sony machines. According to the manuals I've downloaded they don't support writing to DVD-RAM disks, the Pioneer's do.
Important to me as I transfer recordings to my Pioneer 440 using RAM disks as they are left "intact". DVD+RW recordings have problems with the Widescreen flag.
I have to transfer using a Rewritable disk as unfinalized recordings are not compatible. They are compatible between the Pioneer 440 and my Sony 310/710/560 machines.
Another point regarding compatiblity is that DVD+RW recordings will only transfer at high speed between the Sony 310 and 710, but not between them and the 560 or Pioneer 440, have to use "realtime" transfers.
And another gripe about my Panasonic EX77 is that it "physically" formats DVD+R blank disks, which then become unusable on the Pioneer/Sony machines.