Buliding on foundation is un-natural for bees, they have only empty space in the wild. Using foundation is more like fixing bad comb than making new. It does work well for the beekeeper, though, since it regulates the size of the cells better and usually results in better comb (not always). I'm sure the bees make their own comb much faster than "fixing" the cells to foundation.
Foundationless works great with the oft stated caveats -- some bees have to be persuaded into making flat comb in frames. Probably something genetic, they want odd shapes, curves, and forks. Not a problem for them in the wild, but a huge mess in the hive. Those bees tend to make a mess of foundation too, particularly plastic where they sometimes decide to build the comb standing free of the foundation or off the edge of the top bar rather than on the patterned plastic. Just bees.
The other drawback, expecially in the type of weather we've been having here, is that foundationless comb when newly drawn can be very fragile, and until it's attached on all four sides, be careful not to lay the frame over on it's side -- a soft, warm comb full of nectar or brood will simply drop off the frame. It will also likely be too soft to rubber band back in, too! Once it's been in use for a while, it will harden up and be quite sturdy, but the thickness of the cell bottoms is much less in foundationless comb.
I'm using a mixture of foundation and foundationless this year -- last year I did about half and half, and the bees made about 1/3 of the foundationless frames drone brood, the rest worker size, but didn't fasten it to the bottom. Hive got sick, though, so that may have had an effect, too. This year I used mostly foundation for the two swarms I got, but left two empty but crosswired frames in the two mediums I put on. Should be working them about now, so I'll see what they do when they get to them. Last year they make a bunch of drones in late July, but it's so dry this year I don't know what will happen.
peter