A .30-30 is enough for hunting deer, and even bigger animals if you hunt well enough, i.e. you get close enough. (Every cartridge is good enough within its "effective range," e.g. a .22 rimfire will kill a grizzly if you can consistently get close enough and shoot well enough to put the bullet through the eye socket into the brain, but I would not advise it.) The .30-06 is more versatile because it is effective at longer ranges, if you can shoot well enough at longer ranges.