451 rolls better and is faster than 406.
I've had both and even the same bike converted from 406 to 451.
The main downside to me with 451 is tire choice.
Its mainly limited to narrow width tires (road orientated).
406 is better if you are considering the occasional simple gravel/trail riding

Some of the options mentioned are not as convenient in the fold/folded (eg. BF, Airnimal), but they are good in other respects (eg. stiffer, faster, larger wheels)