What's not to like about Dark Mod? Granted, I haven't actually played any T3 FMs, so I'm not sure what's out there, but what do you like better about T3's engine over D3's? Have community modders been able to make huge missions that aren't broken into parts?
My expectations for Dark Mod weren't high, but it definitely feels more like "Thief" than I ever expected it to. They brought back rope arrows, made mantling pretty much perfect, blackjacking is fluid and can be done on the fly (sometimes), sword fighting is challenging, as it should be, and using the bow feels more like T1/T2 than than T3 ever did. There's actually ark and fall to the arrows. T3's bow was too easy to use.
My only complaints are that levels still feel cramped, perhaps slightly more than parts of the T3 campaign, and I that all missions I've played to date don't have many NPCs to sneak by. I read somewhere that the D3 engine can't handle a lot of NPCs too well.
If you have a copy of Doom 3, I highly recommend giving The Dark Mod a try. It's only been out a year, so the missions that are out there can't be compared to the complexity, beauty and size of the T1/T2 FMs, but the potential is definitely there for something great in the future. It's undeniably "Thief"...just a little cramped.
If you have a decent enough rig, I say go for Velvet Assassin. I have two missions to go and I'm up to over 15 hours. Like I said in the thread, it feels much more like Thief than Splinter Cell. Quite challenging at times on the Agent difficulty. It's better than any of the Splinter Cells, but a slight notch under Deadly Shadows.
If what you're asking is if it's different from the Thief Gold missions, then yes. It was made by several Thief-devotees who took it upon themselves to continue the legacy of LGS. Call it Thief III, but with the same engine as T2. New items (EMP bombs, a small hammer instead of your blackjack, and upgrades to all your elemental arrows (once you're given the elemental crystals). Huge missions (museum, trainstation and onboard a train, hotels, tombs)
I've played it through twice in the past year or so. Took me no less than 15 hours each time. You'll undoubtedly be impressed.
What'chu waiting for, Christmas?