Hmmm... I guess it comes down to personal taste. I don't bother with Glenlivet, as I find it to be too perfumey and light (for lack of a better way to describe it). I feel the same way about Glenfiddich. I much prefer The Macallan to either of these Scotches. Glenlivet is the best selling single malt in the USA... probably because they were the first to market single malt scotch in this country... at least in any volume.
Macallan 12 is my regular, every day Scotch. It stands up well against many higher priced Scotches., IMO.
What are you looking for in a Scotch? Peat, smoke., sweetness, salt? Glenlivit is more sweet than anything, at least to my taste. Macallan is way more complex... sweet, (due to the sherry casks)
toffee, butterery, with a touch of peat. If you like Glenlivit, thats great... keep drinking it, but, there are much better Scotches out there.
I'm assuming that you are talking about the mass marketed Glenlivit that is on every shelf in the USA, and not the refined expressions such as: 12 year American oak matured... 12 year French oak finish...17 year cask collection... 15, 17, and 18 years old... etc...