As a support rep, I highly advise against the 34540 release, much has been fixed since then, that release will have issues with SMB scan to Win 10 and Server 2012 (Invalid path, login failures, and file size failures) as well as Scan with Office365 and Gmail (SHA-2 issues).
Latest is nearly always better, trouble is, you need the links to even get the latest as they are not indexed on Xerox.com, luckily for forum users, I have the links to nearly every new version and will post them here when requested, or when I know (or believe) it has the solution to a posted issue.
And as for the version numbers, here are the "decryption keys" as it were for Connectkey and AltaLink, which are the vast majority of the devices being sold. (I don't have these for other families of devices)
I have three different firmware levels in my environment for a WorkCentre 5955:
073.091.075.34540 - Jun 16, 2016
.34540 is the most recent firmware available on the product page and is the most common level among our fleet. .20500 was given to us by a support rep recently to help diagnose finisher issues on recent out-of-box machines, but I can't find any post-upgrade patch information. And .08210 was randomly on a machine that used to have .34540. I believe a service tech may have installed it while on site previously but the machine has been having issues so I moved it back to .34540.
I'm looking for any installation documentation and release dates for these levels. I want to make sure that when we elevate our machine firmware, that we're actually upgrading and not inadvertently downgrading, and that we're properly applying any post-update patches that might be required.