Hubble "sees" different wavelengths than JWT, also, both are overbooked. So we really want Hubble as long as possible, no matter how the JWT launch goes.
Yes, it really matters. It might not matter from the perspective of just making cool looking images, because you can do that in any wavelength. But for science, the wavelengths matter a lot, and you can learn different things at different wavelengths.
Oh no no, i was just worried that JWT would actually not be able to do a deep field 2.0. im very curious on potentially higher details on this and mentioning that JWT and Hubble use different wavelength (or JWT might be able to do more?) would have meant that JWT wouldn't be able to do the same as Hubble in regards of a deep field.