I think you just don't really understand the sort of playstyle that we're talking about.
When I say "I build the farms before I build the boilers", I mean I'm building a 2x2 chunk steve's carts farm with a full RP2 or BC pipe system feeding barrels that feed a fermenter that feeds stills, e.t.c. And when I'm talking about a power system, I don't just mean 5 or so combustion engines. I mean the kind of infrastructure required to produce 300 to 400MJs, including fuel input, on-off switches, power storage, e.t.c. If it doesn't take you 5 hours to design, plan out, gather materials, craft, and build that system, well you just click buttons faster than I do.
That playstyle wasn't decided by any decision to use boilers. That's just how I play the game normally. I like to build large systems and I like to automate stuff.
Look, here's the real reason why I'm still here arguing. In my SSP world I used to use engines for power. They had a large footprint and I was constantly running out of fuel to produce the power I needed. I already had a pretty large tree farm, and didn't really want to build another one. Then I switched to a boiler, ripped out the engines and got more power out of the same fuel production setup. Plus I had more room to put machines and didn't have a cramped basement any more. That's efficiency to me. I just don't want someone else to take your words at their face value, think boilers suck and have to build that extra farm for no good reason.
I get that different playstyles have different needs. The problem is that you seem to keep implying that only a very specialized playstyle would benefit from boilers and everyone else should go for engines. And that's just not true. Not even close.
If you want to talk footprint you are using the wrong farm and biofuel production methods. (At least on Ultimate). I can get several thousand MJ worth of fuel out of 2 chunks of farms (not stacked) and support equipment. (requiring about 300 MJ to keep everything running). Sure using all that fuel either requires a large footprint or a lot of stacking, but the fuel production footprint is nice and small. I also wonder at the space efficiency of your engine setup if you saved so much by going to boilers. A 36 HP still requires 45 blocks just for the boiler, plus room for either a power-converter (you will need to swarm the liquiducts a bit since there is a cap on the steam one face can accept) or 18 engines. This produces the same power as 30 engines. You might get some savings, but it wont be all that much assuming you organize your engines well.
Your argument has now been made as "I like big complicated things and boilers are big and complicated. So, I do not care if they are the optimal solution." That is A-ok, fun is WAY more important than optimal use of resources, but it is not the discussion we are engaged in. Your argument keeps coming back to why you do not care that they are not optimal for one reason or another. That is FINE. It is ok to not take the perfectly optimal route every time. Fk, half the time we do things the hard/non-optimal way on purpose to have more fun (or at least I do). That does not change the fact that "by the numbers" they are the wrong choice almost every time in SSP.