First, skip the .35 Whelen. I have never understood that one when you could have a .338 or 9.3 with a better selection of bullets.
If anyone has a problem finding bullets for a 35cal, in any chamber, they have problems. The old bullet selection argument is a bit thin these days.
I would argue that the .35 has a better selection of bullets. If you are looking for premium hunting bullets, they are available in either caliber but you can buy heavier bullets for the .35. The .35 cal also gives you the ability to load down with softer 150 and 200 gr bullets designed for the .35 rem and to load even softer rounds with .357 pistol bullets for plinking or taking small game.
Most .338 bullets are designed to work at .338 win mag velocities. There are .35 cal bullets designed to work at a broad range of velocities.
There are plenty of .338 bullets that are designed for expansion at relatively lower speeds, such as the ones used with the .338 Sabi in Africa. For example, a regular NOS Partition (not the Gold), Woodleigh, Hornady, and Speer, all the way to 300 grains. One old have to choose the right bullet for the slower .33's, of course.
For example:
http://www.sabirifles.co.za/338sabi.htm
