Engine equalisation would cut development costs massively, figuratively speaking in any technology 95% of the performance is achieved with 50% of the budget, so the big spends are always on the tiny things that keep you ahead of the competition, if everyone is equalised then there is no reason to waste money on developments that get the extra 2 or 3 HP from the system.

The other angle I haven't seen suggested here is that this is a forward-looking insurance play from Horner. At the moment RBPT are winning off the back of development work done by Honda in previous years. Nonetheless, they are new to the engine game and there is likely some substantial concern that when the next engine regs come they will be left floundering.

By backing the equalisation they give themselves precedent to demand the same again a few years down the line if RB engines fall behind the pack. They are likely very confident in the rest of their current package, to the point that they can risk making the current situation more competitive in order to guard against future disaster.

I don't especially like Horner, but I think it's hard to argue that he's anything but an excellent team principle, possibly the best on the grid. If he's doing this there is zero chance it's for altruistic reasons - there is a play for RB here somewhere, it's just a case of figuring out what it is.

I can see a few reasons why I think red bull won't be against this.

1. They believe they have the best drive on the grid. Put everyone in identical cars and Max still probably wins everything
2. They believe their aero package is better than anyone else
3. They were helped by a similar thing a few years ago when Honda was dropping engine manufacturing. Paying back the karma
4. Helps keep costs down. Making an engine be as good as everyone else is significantly easier than making an engine better than everyone else. There becomes a point when it is exponentially harder to increase performance

because they don't really want to make engines and don't want a repeat of 2014 with the next engine regulation change.

equalise the engines and fight amongst yourselves we have aero advantage anyway

this is what it sounds like, Red Bull has Adrian Newey so might as well neutralize the engine advantage that Ferrari or Merc could possibly have