4/4 vs. 2/2 simply determins the macro-beat of each bar. Fast music thats written with the half note as being a macro-beat in mind is usually written in 2/2. Same with quarter notes for 4/4. Often fast music that would look ugly in 4/4 is written in 2/2 to make it easier to read. But, unless you change the tempo markings, you won't *hear* any difference between the two.