True, Kyle's was less painful than the others. But while for most GLs blindness would be a manageable handicap, for Kyle and only Kyle, it was crippling - because he's a visual thinker, an artist, and that means the plan depends on The Enemy knowing him intimately, not just as a GL but as Kyle. That's a significant betrayal of trust, enough to foster lingering damage to relationships.
Tangent: Is it wrong that I kinda want to know what Bats had in those files for Metamorpho? I watched the JLA:TAS episode that gave Rex's origin a couple weeks ago, and watching it I thought, this guy is theoretically unkillable.