NAND or NOR which is better preferred

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among the universal gates(NAND and NOR) which is better preferred and why
 

CMOS NAND is better than NOR as size of all transistors is equal for 2-input NAND.
Size of PMOS is bigger than size of NMOS for NOR.
So NAND layout area is smaller.
 
NAND is preferred because you can create other Logic gates utilizing lesser number of NAND than NOR. That makes NAND the universal gate
 

I like NANDs because I do not have stacked PMOS devices. Anyway I prefer 2input NAND over 4 input which is max. number of inputs in my book
 

2-input CMOS NAND is better than 2-input CMOS NOR, because NAND logic give almost equal rise time and fall time. As PMOS are parallel, so total PMOS resistor will decrease and NMOS are in series, so total NMOS resistor will increase. means in this condition both net NMOS and PMOS will have equal resistor to produce same rise and fall time
 

NAND always preferable in terms of logical effort and speed due parallel structure in pull up circuit.
 

well dynamic NOR is also small and fast. but it has higher activities
 

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