The response curves IMO aren't nearly identical. Take as a reference the flat line from 100 to 500Hz. On the 404 the response keeps increasing from there and get up to 15dB higher than that line at 3-4KHz. All the treble response is above that line. OTOH on the LE all the treble is under that line, as low as by 10dB and the only part of the treble leveling the response from the 100-500 baseline is at 8-10KHz and only by a few dB. That's far from the 10dB higher response at these frequencies the 404 have.
By looking the response curve I'd expect the 404 to be tending to bright, detailed, airy and with a good sense of soundstage. Depending on recordings, even sibilant. The 404-LE should be a bit darker yet still detailed, but not bright nor sibilant.
I must say I had a pair of 404 at home for a couple of months, hence I know their sound a bit, but never listened to the 404LE.