There is a noticeable difference in the "put-down" capability of the .35. As for velocity, there is scant difference between the factory loaded 200gr vs. the 170gr (.35 vs .30/30). Especially inside 75yds as has been noted.
I have both, handload for both, and like both.
It has more to do with the firearm they are in than capabilities of the cartridges.
Either (handloaded) are capable of easily putting deer down at ranges far exceeding most hunters/shooters ability to shoot them.
Bullet selection is very critical to either cartridge.
Either the .30/30 or .35 sighted in 2.5" high at 100yds are zero at 150yds and down approx. 4.0" at 200yds; this gives a 200+yd point blank effectiveness to either.
But, the .35 does have more "splat" as another poster noted.
Inside 75yds, the .35 equals my .30/06 experiences (numerous), as well as .338/06, and .45/70.
I wouldn't want to give up either. My .30/30 is a Glenfield 30, and has a half magazine, and weighs approx. .75lb less than my .35.
If I plan on carrying the gun all day stalking/walking up pigs on a river bottom, I might prefer the .30/30.
But, it really depends on which I just "feel" like taking that day!!!!
My .35 loads get 2,300fps w/ a Rem 200gr Cor-lokt. (slightly over book max. loads w/H4895.
The .30/30 gets 2,385fps w/150gr Rem Cor-lokt over 35.0gr of RL-15.
Both have 20" bbl's.
The .35 has a 3-9x scope for "twilight" hunting in afternoon.
The .30/30 wears a reciever sight for speed while gunning running pigs/deer during "daylight" hours. This way, it weighs more than a pound less than the .35.
YMMV