With today's wide range of premium and standard bullets, the .35 Whelen is better, of course, but only if handloaded.
For soem strange reason the .35 Welen is held to 60,000psi, while the SAAMI specs on the .338/06, identical in every way except for bullet diameter, is loaded to 65,000psi.
That is why you see loads with 250gr. in the 338/06 running mid 2,500fps, while the .35 Whelen is loaded to 2,450fps.

Yeah, I know, that is only 100fps. It's just the principal of the whole cluster - afair.