i ran a heavy CL engine up to my akagi, bit of extra weight doesnt really give that
much speed reduction IMO.

you do have to watch you'r deployment/environment a bit, but hey you're a cv :)

I use Ijn CV engine II-1 (Heavy)
it gives 20/40 knt, it's good for torp dodge.

Bear in mind there are oddities in the game, IE the select few cases where a BB uses a CV
engine (unless this has been changed since I played them). When in doubt too, you can
always try a couple and see which gives the best results. I can tell you when you speed
cap later on, if you accidently put on the wrong engine its pretty quick to tell by
looking at cruise/OH speed in harbor.

Everything Umbrella listed is what to look for in engine selection. Something else to
factor is engine weight, which makes things semi confusing with ships like H39 and some of
the PCAs.

Considering that both have equal cost, weight, OH ratio, and OH time, while the latter has
clearly superior HP, I'm not sure why there would be a dilemma.

The one that will give you more speed.