Dunno about Clan Wars, but previous 2D Worms were pretty much the same as Armageddon. Reading about the features, Clan Wars is pretty much identical, too, but with; better graphics, water physics, more customization, worm classes (4), more friendly interface (campaign and stuff), less available add-ons that you have to pay for them, but in exchange you don't have to work with the fans add-ons unfriendly methods (though inserting user-made maps is piece of cake).
So, yeah, it depends on how much you want friendlier graphics and interfaces (for you and those you'll play with) and if the few perks are really worth it. (Though paying a mere 1$ on Humble is quite silly, but your call). Some new PCs and Windows 7-8 users have a few retrocompatibility issues (like not having the up-page/up-down archaic button to chat online or color issues), everything fixable in unfriendly ways.
Nonetheless, I love Worms.
Warning: Worms is a friends/family multiplayer games, only. Don't expect with Clan Wars, Armageddon or anything to found a "multiplayer community of strangers", it just doesn't exist unless you're gonna invest 500+ hours to compete in the few and time spaced tournaments done. So, if you have friends interested on Worms, play with them. If you don't, it's not worth. Single player is almost null anyway.