Hello,
I have and used: 7x57, .308 W, 30-06, 9,3x62 and 375 H&H. And for a few years, not now, a 7x64. Without having planned I have basically rifles/cartridges with the same external ballistics. I don´t need to make a click in my head because a drastic change in trajectories. I found this a bonus.
About the all around cartridge between them, I must said I would chose the 9,3x62. It is the one I have used the less, until now, but for my needs I see it as the most versatile.
The basic bullet, to me, is the 250 gr. The real basic is the 250 Accubond. I can move to the 250 TSX/TTSX/GMX or my most recent 258 H-Mantel, without any sighting change, for different animals. Also I can use the 220 grs if I want something faster and a little flatter (no too much flatter) trajectory. Or go to some various 286 grs for "heavy work", like feral cattle. But any of those thogher 250 grs are perfectly adequate.
In my case, it is not only the cartridge but the rifle-cartridge combo.
Best!
CF