If I might give my both practical, but also theoretical input on this (hope it does not bore too much, I will leave the calculations out at least...)
windmaker is actually correct, bigger wings will have more lift, but the same amount of more drag (both squared with the speed) - thus almost equal in terms of needed kite - they just go at two different speeds to give the needed wing lift to support the rider, but identical needed kite power.
BUT, three reasons why the bigger wings works better, for smaller kites:
1. There is always some unavoidable drag from the mast and fuselage and stabiliser, which will favor the bigger wing as it goes slower, so the "unwanted" drag (NOT from the main wing itself) will be lower, as the speed is lower.
2. You got a lower "sink rate" (because of lower wing loading, if you got a 4 times bigger wing you will "sink" 2 times slower) - meaning, when there is no kitepower, you can ride longer before you sink down, and also turn tighter thus keeping kiteline tension easier - this is IMO essential for the ability to ride with a small kite, as you are able to do transitions where you will have little or no kitepower when turning, but still stay foiling.
3. Maybe the most essential part is, GETTING STARTED ! As when the board is on the surface, and the mast fully submerged, there will be huge drag meaning, with a really small wing, you will never be able to get the very high speed needed for a small wing to give the needed lift to get up foiling.
Above is the reason why bigger wings works so much better, as Gunnar says, and also the reason why really good riders with super efficient kites can ride with smaller wings - as at some point the higher speed thus a lot more apparent wind and kitepower with faster/smaller wings, will outweigh the advantage of bigger wings..
In marginal winds though, it changes and the bigger wings are better with efficient kites too, as otherwise the wind window will get pinched too much, when riding fast, thus your efficient kite are not in reality efficient anymore.
So yes, IMO and experiences, there is a tradeoff, so bigger is not always better, and there will be a practical equilibrium at SOME size, which I can not "put a number on".
Above is also the reason why, when windy, we can ride with smaller wings a lot better with a lot smaller kites, because now the powerspike is extreme when kite is dived or looped - so getting out of the water and getting quite some speed is easy - thus you get up and ride faster quite easy, thus you get the same lift and can ride just as easy (almost) with the smaller wings, and a lot more fun usually
Hope this makes sense, and explains the very different opinions on this topic