It is either.
Chapter about playable races tells us to see chapter on monsters to see how psi-like abilities work. A box on the bottom of page 184 in monster chapter says that creatures in the XPH are psionic versions of regular ones*. Thus, you can use whichever you choose to.
The way we dealt with this when we were playing / I was DM in a club was to decide up front if campaign or adventure was using psionic or not, and then we were using psi or regular versions exclusively. Mixing them didn't sound like a good idea, but admittedly we never found any rule preventing that.
Exact nature of the ability does not matter by default. Page 55 of Expanded Psionic Handbook defines psionic-magic transparency as default rule. If that's the way you play, effects that affect spells and spell like abilities works just as well on powers and psi-like abilities. Of course, there is a "psionic is different" option that would make it matter. In that case, I strongly suggest using only psionic variants of races and monsters that have such variants, because mixing them becomes extremely confusing for players.
* If you want to nitpick, it only says so about creatures in monster chapter, but there is nothing about that matter in the playable races chapter, so this seems to be pretty reasonable extrapolation.