How willing are you to take the chance that you leave something important behind? Besides, whoever buys it from you would probably like the fresh install assuming they aren’t planning to wipe it clean themselves.
There’s your software, email setups, internet favorites (and cookies) as well as other temp files, and all your actual data. Some of this might be deleted by zapping your user account but a lot of it might not be.
If I were selling my TR3A, I would run the restore, then run a program like BCWIPE on the drives to make sure there was absolutely no trace of my data.
It’s not like 9 discs are that expensive. If you can, do it and run the restore. Then you will be sure none of your data is there and you can hand over a factory fresh install.
You can even be nice and include the discs with the machine when you sell it.