I like setting up the complex systems that keep everything running. Balancing the input of the various farms, or setting up a automatic cut-off when I can't. I dislike grinding for the sake of grinding. Especially if there is absolutely no way to automate. I played magic farm 2 for while with hard core and the foodie configs, and I found everything nice and difficult. It had a steep learning curve, but once you learned it, it wasn't really all that hard. I ultimately stopped playing it though due to the random infernal mobs. You could do absolutely everything right, yet still die due to an ender creeper or some such ninja/rust zombie with regen. I don't mind dying due to my mistakes, but when you die on hardcore purely due to RNG, that takes the fun out of it.
I haven't played with GT since 1.5.2, but what I liked about it was that *everything* had a use. You could ultimately spin any resource into energy or another more valuable resource with some time and ingenuity. Some of the manipulation chains were downright long and complex, but it could be done.
Right now, I am playing a mix of magic based mods in 1.7.10. Thaumcraft, Blood Magic, Botania, Witchery, Twilight Forest, Forestry (and Binnie's Mods), Buildcraft and Railcraft plus a few cross-over mod add-ons. I added in Chococraft (dungeons) for a little added difficulty, but have yet to find a dungeon
. I am considering adding in Zombie Awareness for a bit more challenge, but that would likely break the dungeons with Chococraft.
I don't mind difficult mobs (like what natura does with the Nether) but I dislike it when the difficult mobs are everywhere. It doesn't give you a peaceable area when you just want to build.
I guess my favorite mods are ones that you can't get access to all at once, and don't arbitrarily hold things back behind the need for a mass of diamonds or ender pearls, but have other limitations in the game play, hence my current pack. Nothing is locked behind a wall of diamonds, yet everything will take time to unlock and build.
I've played my current world for the last couple days, and think I'm going to start a fresh one despite the time I've put into it. The worldgen is just kinda blah. I've wandered in about a 2000 block wide circle and have yet to find a desert or magical forest. With starting over, I'm thinking about adding in Deadly World along with Pam's Harvestcraft, Hunger Overhaul, and Spice of Life. Mining and running into a silverfish vein may lead to a hasty retreat, but shouldn't kill me outright. It should keep me on my toes, and up the engagement factor a notch or two. I've actually grown rather fond of Pam's Harvestcraft between Magic Farm 2 and AgS, and like all the different food choices available. This doesn't add any real long term difficulty, but will give me a focus during my early game while I am building up resources and planning a base.
Side note: I will likely add Natura back in just for the more dangerous nether, but can anyone recommend any mods that add in dungeons/overall mob difficulty without the craziness of infernal mobs?