Welcome to LRH.com and the addiction!
There are many things to consider when trying to build a long range rig. From you caliber choices a custom or semi custom rifle is your best bet. You can buy the 6.5x284 from Savage as a factory rifle.
However I have to agree with Oliveralan. He speaks the truth that both are barrel burners. With either cartridge you are looking at a life expectancy of 800 to 1000rnds. of accurate firing. Maybe less depending on barrel care and potency of your loads. I also agree with his caliber selections for learning on as well. Both calibers will force you to learn how to read the wind and learn elevation dope.
Some other calibers to consider would be the 6mmbr, 22-250 (fast twist), 243/243AI, 260/260AI, 6/6.5x47 Lapua, 7mm-08, and 6.5x55 Swede. These are all great starter calibers to get you to 1K for target. These will all provide better barrel life than the two you originally chose. Those calibers would be great for later when you are capable of shooting very well and consistently to long distances. Another thing to consider is application... target or hunting? If hunting how far do plan of shooting and what size animal. If you want to go to Elk at 1K then none of the above will work. If you want to shoot paper to 1K then all the calibers above will work. Just some other things to consider.
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