The 42t will make the bike more sluggish feeling at lower rpms.
The trade off is a higher capable top speed; however you would need the ecu restriction removed, and perfect conditions to see a potential top speed approaching 200mph.
Your highway cruising rpms would drop around 200 rpms.
The wheelbase will be slightly longer.
The bike will need more effort to lift the front tire.
Maybe, maybe you get another mpg or so out of the bike.
Not a lot of practicle application.
A 46t rear will shorten the wheelbase slightly. Upper limit cornering capabilities will improve a little from this.
It will take away top speed, but you should still easily be able to go low to mid 170s(mph).
The front tire will lift with ease, especially 1st and 2nd.
The bike will accelerate quicker, and the midrange will feel much stronger.
Lower et's at the dragstrip are possible.
It all comes down to your riding style.
If you just like to cruise or commute, the 42t is fine.
If you like an aggressive feeling bike to play on, then the 46t is a noticeable improvement.
Either work with the stock length chain.