I think, though, with all the work that goes into it - you're better off simply backing up your files and do a clean install om Mint 13.
If the time needed were the only criterion, then weblave's conversion is much faster than a complete new installation from the scratch.
My Precise Pangolin which I used as the guinea pig was absolutely up-to-date, including kernel 3.2.0-32.
A small number of additional software, all coming from the official repositories, had been installed.
A little bit of personal tweaking and configuring has been applied.
If I install Linux Mint 13 Cinnamon from the scratch today, what I will get is a system as it was way back at the end of May 2012.
Next Linux Mint 13 will pull roundabout 400 updated software packages and install them. As my internet connection is limited to 5 MBit/sec. the update alone will run for more than an hour. Depending on the time of day and on the speed of the machine used the whole update procedure may take up to 2 hours.
Then I will have to add another 20 minutes to go through my list of extra software and install the programmes.
Finally I will have to restore my data backup and - more time - consuming re-storing my personal configuration.
So all in all an installation from the scratch will take no less than 4 hours
Applying webslave's conversion took me 1 hour
. And my system is still up-to-date and all of my personal settings which are independent of Unity vs Cinnamon are still valid and present.
So if it were a matter of time only, then converting would win.
Of course, however, there is a certain degree of uncertainty as to whether in the course of this conversion,
- all the needed software packages have been added
- only the no longer needed software packages have been removed
- any garbage may have been left behind.
- all necessary configuration changes have been applied.
It has still to be verified that the result of the conversion process is a consistent Linux Mint 13 Cinnamon system.
Therefore, if this system were vital or me, I would definitely take the longer way and install Linux Mint 13 Cinnamon from the scratch, apply all updates, re-install my additional software, recreate my personal settings and restore my data files.