Thanks guys, that was exactly what my original question was about. Like I already said, skip the considerations for time to taxi/duty day and all the other endless excuses. The question is based on using the max derate and ATM on each runway length.
Subject to confirmation, may feel better to use the longer runway but now you are reducing the thrust even more for the takeoff. So assuming that you are not at maximum derate/atm, it appears that there is no more margin for an RTO or accelerate-go as there was on the shorter runway.
Then again, if it is a really long runway, then perhaps it is safer.
Is this correct?