There's quite a power difference between the two. The 35 Rem is a short range deer & black bear round while the 35 Whelen is a longer ranged round suitable for all North American game animals.

With Remington Factory loads the difference is 1921 ft-lbs at the muzzle for the 35 Rem vs 3177 with the 35 Whelen. Thats comparing both with 200 gr bullets. Remingon also loads a 150 gr bullet in the 35 Rem and a 250 grainer for the 35 Whelen, which further accentuates the difference.