If you read the manual and your first post with more attention, they say:
"depending on the input level setting"
To accomodate a +4dB line level signal on the 1/4" you'll have to attenuate the input level of the Eventide or you'll get distortion in the red.
The two plugs are wired differently and use separate electronics in the signal path. The XLRs have a much higher headroom and thus can accept high level signals.
best
I
