Venger:
All depends on what sort of gaming experience you're looking for.
Apolyton: Let's you play CTP2 the way it shoulda been from the box.
Cradle: An awesome mod which is almost a total rebuild of everything. This is where most of the work is being done.
Med pack: A medical pack to fix a lot of bugs in the outa the box version, plus a lot of new additions.
Agreesiveness levels:
Cradle: Hold onto ya hat, cuz you'll get your ass handed back to you on a silver platter. VERY warmonger!
Apolyton: The middle-range. Agressive AI when you piss them off, but allows more for the "other" victory conditions.
Med pack: The least aggressive of the 3 big mods.
Other mods:
The three above mods are complete seperate mods. Hence why you need modswapper to switch between the three. The other mods you'll read about (goods mod, citymod, diplomod, AI PW mod, AI commerce mod, etc) are add-ons for these mods. You'll find that nearly all are compatible with the 3 big mods, maybe with a little helping from yaself. The add-ons attack one specific part of the game where the big 3 change/fix the WHOLE game.
Hope this helps.
All:
BTW, it's good to see the CTP2 forums still ticking over.
Expect a lot more traffic in here as Civ3'ers swap back.
Myself, I'm over Civ3 too now. I'll float around here, but with the development of my own game won't MOD stuff for CTP2 anymore. But I'll around.