Siv HD ap reksai

First: She.

Second: Ult is not an escape, as any damage stops the channel.

Third: Nidalee also has an escape (Since she can pounce over walls), and a move speed beef, and better sustain (Since Rek'sai needs fury for her REALLY SMALL heal and Nid can just... heal, which ALSO gives her a move speed buff).

Fourth: Nid's spears have a lower base damage and scaling, which is more than made up for by the ability to get triple damage.

Fifth: AP means you are only utilizing one ability from her kit. It means you aren't taking advantage of the aoe mass fury building part of Q, it means that you the knockup form your W is laughable, and it means that your true damage attack is basically meaningless. I dunno about you, but 120% AD true damage sounds better than 'build MR'.

Also, don't forget that Nid can revealing people for 4 seconds in a variety of ways (Gaining a lot more move bonus than Rek gets). Nid is faster, has more ways to escape, does more sustained damage, has the ability to do sustained burst damage, has better sustain, is better at sticking to targets, and can prevent vision juking easier and for longer.

If someone wants to ignore an entire kit for one half of one ability, and that's so OP, let's go back to the days of AP Sion.