You are confusing memory addressing with audio engine. Both are measured in bits, but have absolutely nothing to do with each other.
A bit is simply a "binary digit", 0 or 1
1 bit gives you two states: 0 or 1
2 bits gives you 4 states: 00, 01, 10 or 11
3 bits gives you 8 states: 000, 001, 010, 011, 100, 101, 110, 111
etc etc etc.... each extra bit gives twice as many states as the previous amount of bits
8 bits gives you 256 states: I ain't typing these out!
16 bits gives you 65,536 states
32 bits gives you 4.29 BILLION states
64 bits gives you 18,446,744 TRILLION states (gulp)
For memory addressing, 32bits can handle up to 4.29 BILLION Bytes (approximately 4GB). With today's computers being able to fit more RAM than this, it's a shame that any given 32bit application can't "see" more than 4GB RAM. It used to not be a limitation, because who the hell had more than 4GB RAM several years ago? An imaginary 33bit application could see twice this RAM: 8GB. An imaginary 34bit application could therefore see 16GB RAM. A 64bit application (actually, it's really a 63bit application) can "see" 9 ExaBytes (9EB) which is 9,000,000,000 GB. I don't think all the RAM in the world adds up to this.
So far, this has absolutely nothing to do with audio engine or sound quality.
Logic's audio engine (as is the case for most other DAWs) is 32bit float (don't ask about the "float" part - that's another discussion hardly relevant to this one). So there's 32bits worth of data that makes up the audio stream inside Logic. Even without the "float" part, that'd give you 192dB dynamic range (each bit gives you 6dB of dynamic range). No physical device could ever achieve this, nor does this range (quietest to loudest ratio) probably exist on earth. And the "float" part makes it even bigger than this.
Are there any DAWs with a 64bit audio engine? Would it make an audible difference? ProTools HD (not LE or MPowered) uses a 48bit fixed (not float) system.
So you can see that measuring two different things in "bits" has a very different result:
--For memory addressing, each additional bit DOUBLES the total amount of addressable memory.
--For audio engine, each additional bit adds 6dB of dynamic range
Comparing the two would be like comparing cheese with granite because both could be measured in grams.