Having only shot two elk, I ain't no expert.  But I shot mine with a 6.5 x 55 and both were DRT.  Personally I would go with the 30-06 in a light rifle, mostly because of a Winchester m-70 featherweight in 7mm magnum that I once owned that was the nastiest kicking rifle I have ever owned.  Spoiled me on 7mms I guess.