Which Moltres to spend 86 RC and 96k dust on?

15-10-14 and its not even close. Bulk points are not so important in my eyes, if you give up HP for it. You will be guaranteed the 2 extra HP, but not the 1 less damage per quick move. The 15 Atk is another nice bonus.
Note that Charizard with Blast Burn (seems likely) is right around the corner and it could dethrone Moltres as fire type DPS king, so maybe hold on to it till the community day is over.

Don't spend until we know how good BB Charizard is.

If you want to power up regardless of the risk or BB Charizard ends up being worse, go with the second one. 15A is much more important than 1 point of overall IV when you're not maxing, it'll reach breakpoints faster and save you RC and dust.

Edit: Personal preference.
That extra point of attack doesn't allow you any extra dmg breakpoint with the current/future (short term) raid bosses (the regis). However, in this case, you reach a dmg breakpoint and a potential bulkpoint half a level lower with the lower IV one. But both of them reach the same bulkpoint at the level required for max dmg breakpoint (34.5 or 35).

I sum up to the "hold on warning". Charizard's CD is not too far away, it may be worth to see how good will it be with a new special move.