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A 4:1 MUX can be built by using three 2:1 MUX. But I've not done it this way: I've used a 2:4 decoder to make a 4:1 MUX. Does it matter? enter image description here

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closed as not a real question by Wouter van Ooijen, Brian Carlton, Olin Lathrop, Dave Tweed, Leon Heller Mar 10 '13 at 3:37

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Matter for what or to whom? (in other words, this is not a real question.) –  Wouter van Ooijen Mar 9 '13 at 20:48
For an ALU or to measure a time difference due to propagation(?) –  Niklas in Stockholm Mar 9 '13 at 20:53
I your are optimizing for delay time you must first decide whether it is an address change or a data change that is your starting point (or maybe the maximum of the two delays?). After that, I think you can count gates yourself? –  Wouter van Ooijen Mar 10 '13 at 9:22

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It matters depending on what you optimise for. Your way is probably better once you factor in the extra cost a higher part count causes, and the fact that a single chip solution is likely to be faster than one involving 3. For most purposes, there isn't too much of a difference. Though, I will note that your schematic and actual application are important pieces of information required to pass specific judgement.

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