Maybe the narrower board wouldn't do as good of a job deflecting stones?
I'm not fully convinced on the effectiveness of running boards protecting the paint on the doors, as my 02 had running boards AND mudflaps when I got it and the paint still has some wear. I've since removed the boards as they got in the way for me and the stock boards on TBs are plain ugly lol. I still have the flaps.
I was wondering the same thing. It looks they don't hug the car as much and you can see the mounts where as the factory ones there is no gap.
As for the effectiveness, here is my logic:
Our very first Rainier had the oem moulded mud flaps on all four wheels but no running boards. The Rainier has tons of cladding and the cladding had the sand blasting effect on the lower portion of the rear doors.
Our second/current rainier had the OEM running boards but no mud guards and has none of the rock chips/sand blasting. I added mud guards all around anyway when I got it at 46,000 miles so nothing flicks up at my boat. Without the front mudguards, slush collects on the running boards also in the winter. Since I just paid cash for the 9-7 which was fine but I just got the out of state title for it so had to register it in MN and had to pay the insane MN sales tax and several hundred for plates and tabs. Most of the money I planned on using for mods is now in the government's hands. Now add xmas presents to that, getting my snowmobile fixed and a bunch of other stuff so I'm playing the running boards by ear.
Today I will try to add an extra pair of mudflaps i've got in the garage to the front wheels of the 9-7 for now until I decide.
I do really like the look of these runningboards especially with the chrome caps.