When included in the initial design:
- you feel holes in the road less, less vulnerable to falling into potholes, longevity
- find more compatible gearing: needs to be multiplied less (spin less) to achieve a given speed

When upgrading from 406 to 451:
- not a good idea: you will change your steering geometry and handling. it will increase "trail".
- changing only one wheel, an even worse idea: you will affect head tube angle which puts everything about the initial steering geometry out of whack.
Why are those bad ideas? Riding hands free could suddenly become a very dangerous undertaking or the bike's handling could become very sluggish.

However, if the initial design is flawed (ie: the " actionbent recumbents steering flaw"), using a larger wheel and tire in the front could sometimes help reduce a faulty steering geometry design that caused the bike to be very unstable and not rideable hands-free in the first place - but this is not a universal fix for all bikes as it all depends on the combination of trail and/or head tube angle you are trying to fix since all are affected.