Did you notice that they did not compare any of those to the Nosler Partition? I have hunted with Nosler Partitions ever since Nosler quit offering the Solid Base bullets and replaced them in the lineup with Ballistic Tips. So in the last 15 years I have harvested 9 animals with Nosler Partitions, weight retention and penetration were superb, and accuracy is as good as the rifle will deliver. All this for about 40 cents per bullet. Compare that with some of the premium bullets on the market, and it's downright cheap. Barnes TSX are over $1 ber bullet, MRX are almost $2 per. Nosler Accubonds are about the same cost as Partitions. Combined Technology bullets (Nosler + Winchester) are a bit more. Swift Sciroccos are over $1 per, and A-Frames are over $1 per. All of them perform admirably and as advertised. But, in reality, for average game animals at average velocities, WW PowerPoints, Rem CoreLokt, Sierra GameKings, Hornady Interlocks, Speer HotCor, Nosler Ballistic Tips all work well, at very reasonable costs per bullet. If you feel you need a premium bullet, buy some and use them, but there's no need to mortgage the home for a few rounds of ammo.
A 6.5mm bullet will kill elk just as dead as a 270 bullet (.264" vs .277" bullet diameter). Elk are not bullet-proof. Just shoot them where it counts. The fact that your 30-06 bullet killed your deer and did not exit just shows that the deer was still dead. Don't lose any sleep over it. If you are worried about the 6.5mm (IIRC yours is a 6.5-257 Roberts), just use the 30-06 again.