Well for me (user of Pro since the beginning), using the https://www.gpsoft.com.au/program/pro-lite.html comparison list as a cheat-sheet (never used the Light version) are these:
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Windows Explorer replacement including desktop double-click to launch
Opening folders directly from Explorer desktop or anywhere else in shell opens them in a new tab in Opus, very convenient and tidy. -
Completely configure the user interface including the default toolbars, menus and icons
I don't know in what way exactly it's limited in Light version, but I have adapted & organized the UI of Opus to my workflow; added my own buttons, menus, commands and custom toolbars relevant to me etc. -
Improved file management functions including recursive filters, secure delete, UAC administrator mode, multiple undo levels and logging- The advanced filtering is so powerful it's crazy. I don't know where to begin describing it (especially since I don't really know in what way it's limited in Light version).
- UAC administrator mode enables "surgical" administration of protected files without pain.
- Multiple undo levels are in a clickable list so you can undo something specific (delete, rename, move, copy etc.) from a specific out-of-order sequence if desired.
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Synchronize, Duplicate File Finder, file Split and Join functions
While yes, there are better stand-alone utilities for these operations, for ad-hoc stuff when you need them, they are there, nothing third-party to install. Especially convenient on portable version of Opus. I often used Synchronize with advanced filters to automatically sync work stuff on my USB stick (it's fast because it doesn't blindly copy everything, only changed files). -
Create complex multi-line scripts and add your own commands to the existing internal command set
I have lots of my own buttons and menus which can do complex things and they boost productivity for both in-Opus and outside-Opus tasks at home and work. At work it allows me to have complex things processed with one click and minimal keyboard data entry instead of multiple steps and running external scripts/programs thus reducing the stress when there are crazy deadlines. -
Full Active Scripting-compatible scripting interface
This is extremely powerful and I can't describe it without writing a wall of text nobody would want to read (even myself
). -
In a nutshell it gives you the power of "real" programming languages (jscript, vbscript) right within Opus. You can even access the Windows API to control any aspect of Windows OS (for example stuff like opening the CD-ROM drive tray can be done with only a several lines of code in Opus button).
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You can also create (and use existing) Add-Ins to alter the behavior of Opus itself so you are not at the mercy of the Opus developers for them to implement some tweak just the way you want. See this example (note: there are probably better/more interesting examples).
But anyway, with Opus (Pro version at least 
) there are 1001 ways to accomplish things and anyone can do it the way it's most convenient and easiest for them.
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Read/write support for archive formats other than ZIP
I mean who uses ZIP anymore with 7zip & RAR in the 21st century
In fact since Opus uses 7zip internally it supports all the formats 7zip supports (including ISO, VHD virtual hard drives etc.) thus you can directly enter into all these archives as if you're entering into plain folders. -
Integrated FTP support
Useful for ad-hoc access to FTP servers (and mobile devices wirelessly) with all of Opus' advanced functionality available (as opposed to using FileZilla separately). -
Native support for portable devices (MTP) like phones, tablets and cameras
This one's easy: full Opus power available when browsing your phones, tablets and cameras. -
Integrated metadata editing
TBH I prefer the separate MP3tag utility for this, but you can still use Opus to edit/add all kinds of advanced tags of multimedia files you probably didn't know are even supported by them! -
Use Flat View mode and File Collections to better manage your files
Another feature that could make me produce a wall of text, but you have to see it (and it's sub-features and the way additional stuff becomes possible in combination with it) in action to fully appreciate it. Try to take a look at this explanation. -
Create stored queries using Windows Search for instant access to complex search results
Examples for this could be endless. One example would be to have it as a shortcut to display all your 5-star rated songs which are otherwise scattered around the hard disk. -
Priority technical support, discounts on future major upgrades
Yeah, as a Opus Pro user since Opus 10, I have to say the upgrade discounts were always pretty nice.
I've probably missed lots of other stuff (luckily?! ).