IMHO, the traditional can or traditional can with efficient bulbs can be one of the larger hidden energy losers in a house, in that they typically are not easy to impossible to seal against air movement. With warmer air trying to escape the ceiling, they let a lot of air out of the conditioned envelope. This is of course tempered by whether the top of the cans are in the attic, have an insulation dome to stop air movement, etc., but it is something that should be looked at to ensure that you don't lose a lot of heated air in the winter.
There are newer cans that are low heat generating, so they can be sealed, and I wouldn't use anything else to make sure that air infiltration (the stack effect of air moving higher from the basement through the house and into the attic) is minimized. I would advocate that making sure that the conditioned space envelope is well sealed is the most important factor in energy costs, followed by insulation factors. It's the reason that spray foam is as popular as it is, as it greatly aids in sealing the conditioned air envelope.