Hi,
Like Bob I did the helicopter ride into and out of the canyon and the boat trip when I did the Golden West trip which was about three years ago, but I went back to the Grand Canyon about 18 months ago and they were no longer allowed to fly helicopters into the canyon. You could take a helicopter or plane ride over the canyon but no one could go below the top of the canyon.
As to whether to go by helicopter or plane, the helicopter tends to fly lower than the plane but the helicopter takes up to six passengers, three per seat, and if you are sitting in the middle then your view can be restricted. The plane flies higher and I think you get a better overall view of the canyon. Also in the plane each passenger had their own seat by a window.
I didn't try the horseshoe walk as our guide said that some people were disappointed by it and you aren't allowed to take your camera with you.
Regds
Jim