Actually 2^64 vs 2^32 (64^2 is 2^7, 64 is 2^6, 32 is 2^5)
Other things equal, 64-bit should take twice as long because it
takes 64 bits to do anything instead of 32 bits.
Not really that simple, because accessing 32 bits can involve
1) accessing the 64 bits that the 32 bits are in.
2) selecting the appropriate 32 bits of the 64 bits.
The 64-bits does affect how big the swap file can be without
resorting to Rube Goldberg contraptions to identify what is what.