No far off mate.
In general at an F1 test you get much much more access. In fact, I was really surprised at how open the Circuit de Catalunya was.
You’re also right that tickets are cheaper. In addition, traveling in February proves to be good value in comparison to the rest of the year – especially if you book early. For me another attraction is Barcelona, I’m a big fan of the city and know it well. So combine that with an F1 test and I’m sold.
Finally, from photography point of view I should point that there can be a lot less track activity than say a GP practice session. You often find yourself hanging around waiting for the next car. Each team only runs a single car and box frequently. In once sense that’s good as you can experiment with a lot more view points. However, if you’re practicing a particular technical or style you might want a bit more track activity!
Hope this helps :)