If it's going to be purely target shooting, higher magnification will usually be your friend.
If you will be doing any hunting, I would recommend a lower setting.
I used to prefer very high magnification even for hunting, (scopes in the 8-40x range) but as I have progressed, and started shooting further and further, beyond 1 mile and now ready with a range out to 2 miles now, I have actually lowered my magnificatiim settings.
It comes down to personal preference and practicality, but as a general rule, I would say that the minimum magnification for a given distance is about the distance multiplied by 10. 1000 yards - 10X.
Personally I use scopes in the 24x range but often wind down to 20 or 18 when shooting steel to get a clearer image, less mirage, and when hunting, I tend to try to use the lowest mag setting I can, so I can keep my sight picture easier, spot and react quicker and easier.
Even when I have to use all my clicks and wind down to 6X to get 15 MILS more elevation, I don't really suffer shooting at extreme distances with low magnification.
But it all comes down to the point where personal preference meets practicality .