You can buy factory ammo for the 9.3x62, somewhat easily, depending on where you live, but it's almost always 285 or 286gr, all running 2200 to 2300 fps. Though you can sometimes find Nosler factory 250gr loads, which are pretty wimpy and run around 2400 fps, at least in my 24" rifle.

You can buy ammo for the Whelen, in my experience, much more easily, and in more places. There are several very good and commonly available 225gr loads2700 fps (Fed trophy bonded and Nosler accubond), some 250gr loads2450-2500 fps (partitions, here and there, and corelokts), a ton of 200gr loads at 2800-2900 fps (TTSX, corelokt, federal fusion, Hornady) and one common 180gr load (TTSX) at close to 3,000 fps.

There is no factory ammo for the 338-06.

If you're shooting something that needs a 286gr bullet at 2200-2300 fps, it's an easy choice.

If you want the option of shooting factory ammo from 200-250gr, you're probably looking at the Whelen. The 225 accubonds have a very thick copper back end and a very soft front end. You'll probably get expansion out of them out to 500 yards if you're in the mountains. I've run them to about 750 yards and they were still flying straight. The 225 Trophy bonded are a little harder and tougher.

If you're handloading, the 9.3 will show the biggest difference between the factory loads and what you can handload, often 200-250 fps.

Most of the Whelen factory loads are either at or fairly close to full pressure. You often have to use fancier powders or really step on it to get much faster what you can buy pre-made.

Long winded but hope that makes sense.