for me, depending on the body size being considered & the 12 strings models i've played/owned
the 455ce seemed to have a slightly more balanced tone, but the 356ce still gets 'the nod' (imho)
the current 300/400 series shows to have fiber listed as the heel cap material, which is likely the
same as the binding, although earlier models have used plastic & 04-06s has unbound fretboards -
the original 91-97 400 series had black binding, which was also used some LTDs models (00 LOTF maple)
up until this year, the aesthetics, other than the binding, on the 300/400 series was the same -
large 6.33 mm MOP dot fretmarkers were used on both series, while the current the 300s have
4mm pearloid dots & the 400s have engraved 'progressive pearloid dots, so the change was recent
the difference in price between the 300 & 400s & the XX3/XX4s is roughly the same & seeing that the acoustic,
non-cutaway series has identical aesthetics in the 3 & 4s, the upcharge seems to be purely for the different
tonewoods & could be related to the differences in the process required from start-to-finish (wood-to-guitar)
on-the-other-hand, if both the 300 & 400 series had identical appointments, & pricing, the difference
would be in the tone & what the individual player prefers (which is the way it is on the acoustic 5-8s now)
pretty much everything being discussed here is subjective -
one likes what one likes & there is no 'right-or-wrong' answer
i believe that respecting each others opinions & agreeing-to-disagree is needed,
rather than trying to continually hammer away on a point where there is no 'winner'
ymmv