I like a little bit more fat than the whole milk. 5% to 6% seems to create the most sweetness and the best mouthfeel. To get there, I either use a pint of 2% with a pint of half and half, or a quart of whole milk with a pint of half and half.
There is an issue of the extra fat interfering with the taste of the coffee. My feel on this is that there is absolutely no relation between a good espresso blend and a good cappa or milk blend. For milk blends, it's best to use the coffees one finds at Viennese cafes for coffee with whipped cream or for breakfast cafe au lait. Mostly, these are medium-dark roasts using Bourbons or Kenyan SL28s. If you want higher end flavors, you'll need a melange of dark and very light roasts. The best shot for the high end is coffees with pit fruit, rather than citrus or berry, flavors.
This advice applies only to shorter milk drinks like machiatos, cortados, or 5 ounce cappas. For coffee flavored milkshakes, all bets are off.



