No problem. I like this thread.
The .308Winchester is virtually the same as the 7.62x51 which is the official NATO round.
The 7.62x54r is the .308win of the communist world during the cold war.
The 7.62x54r is a tad longer and rimmed but virtually very similar. The problem is that the 7.62x54r in military version is mostly metal cases and metal core whereas the7.62x51(.308win) is brass with a huge array of possibilities and widely available brass. The 7.62x54r is not more powerful, it is actually a lower pressure case, so the .308 win can be also pumped up and loaded with 180gr and even 210gr loads but like the russian then it is not going to be very flat shooting.
I am not a 7.62x54r expert but the .308win I shot a lot in the service and then as a veteran for almost 30 years and I can assure you it is a very reliable/consistent round. It is standard issue in NATO and here to stay for a long time. Very forgiving for re loaders and is cheaper than the 7.62x54r if you reload. Also the options of high quality modern rifles is amazing. Probably the biggest assortment of options and very popular around the world where is legal. Where is not legal the people use the cartridges based in the same case that is the .243 winchester, 7mm.08 that are also huge world wide along with the 30.06. The .338 federal is also based on the .308Win case and there are also great factory loadings in 6.5mm and other calibers based on the same case. Same thing applies to .30.06. The reason they are popular and they have been proven through the years.
Those loads are manufactured here and will never be sortages of loads and brass. The others, we do not know what the future will bring.
If it was me, based on the selection on the .308 caliber department I would keep it simple with a nice .308 winchester or .30.06. It might be popular and thefore not exciting and neck turners but get the job done well and better than many other cool offerings. Everyone should have one of those if not both.
Keep it simple.
Also when extra punch is needed look at the speed and energy of these new loads. They don't tell but you need long barrels as they are slow burning. I was playing with some of this new ball powder today and I need to go longer. In any case more than plenty for anything here in America.
http://www.cheaperthandirt.com/61119-5.html
http://www.cheaperthandirt.com/72028-1.html
These will cover 99% of the situations of the average American hunter.
More speed, more grain than 168, 180... totally unnecessary.
Cheers,
E.