I tend not to add Rotarycraft etc to a first playthrough of a modpack since it kinda takes over everything (especially my iron), but when it's in I prefer it for Steel. After that...I'm currently playing Horizons Daybreaker. Mekanism is reasonably efficient and somewhat fast, if slightly annoying (there's probably a good way to automate it, but I haven't really looked for it), but honestly I prefer the QuantumFlux crafting version of 1 iron with 4 coal in the corners. Similar to the MC1.6.4 Universal Electricity recipe, and while it gobbles coal, I'm not exactly using it for much else.
The Railcraft/Immersive Engineering Blast Furnaces are way slow, as far as I'm concerned. I'll use the Coke Oven because I need creosate oil, but that's it if I have other options.