GTR Evo and Race are virtually the same! Evo has the Race07 files included and offer a slight edge with a few options and a little optimizing. I would not have a computer without Evo.
That being said, I would not have a computer without GTR2 either
Evo with Race )& and the STCC are a fantastic combination... and they're are many add-ons for this game including many many liveries.
Also the GTR2-to-Evo mod is a great mod which brings all stock cars from GTR2 to Evo.
Plus, mods for Evo are just as easy to install.
For me, the price is a no brainer... at about 40US for Evo with Race07 and then STCC (STCC offers a great forced pit stop and super pole option I love)
Evo also offers closer offline racing vs. the AI and the AI can be set to very high levels to challenge anyone IMHO with all assist off.