The 4.5-30x 6500 has very limited vertical adjustment, about 50 moa total, which won't allow you to shoot to the distance potential of the .300 RUM. If you were to go with the the 2.5-16x 6500 then you have about 80 moa total vertical thich is substantially better.
The Nightforce in comparison has 100 moa vertical for the 5.5-22x and 120 moa for the 3.5-15x.
As far as glass, the 6500 is reputed to be the equal of the 4200, which means it's quite good, but I've never heard anyone venture a suggestion that it is as good as Nightforce.
I had a 6-24x50 30mm 4200 Bushnell that was a nice scope, but I truthfully found anything above 18 power or so of limited usefulness. I sold it and were I to get another to replace it I would go with the 2.5-16x50.
IMHO, if you can swing the money to get a Nightforce you will be far happier with the performance and it'll be a much better choice overall. Also IMHO, if you go with the 5.5-22 you would be well served to get the 56mm objective.
I suggest you spend some time over at Snipers Hide in the optics section to get an education on long distance optics.