Ready to format/partition a 120GB SSD that has been securely erased by use of hdparm and install Ubuntu Studio 16.04 (currently running from a live USB).
Should this be done via the Ubuntu installer itself , GParted or the gnome-disks utility perhaps? Are there any pros/cons?
The recommended/easiest way is to boot Ubuntu (Studio) from the live USB and either simply let the automatic installer (install Ubuntu 16.04 and let the installer do the partitioning for you) or, when it asks you how you want to partition, click 'Something Else' and use the installer's manual partitioner that comes up. Naturally I would expect that you would know what you're doing if you take that option!
I think you can also try running GNOME Disks from the Live USB if you want to try that. And you might be able to install Gparted to the live USB to run that (apparently you need to select 'stored in reserved space' when creating the live USB via Startup Disk Creator to do this) or you can use Gparted Live to partition the SSD beforehand, but this is more complex.
Really, just use the installer. I can't give any proper run-down on pros and cons (you'll need to wait for someone else to answer if you want that) but I can say that using the installer to partition is recommended and probably easiest.
If you have any serious problems (by this I mean a proper issue, not "I don't like how the installer does this") with partitioning with the installer, then try and reproduce the problem by running the installer after clicking 'Try Ubuntu' (instead of 'Install Ubuntu) at the start and running the
ubuntu-bug ubiquitycommand in Terminal preferably after reproducing the bug (make sure you've connected to the Internet). Then the developers can try to fix the bug.