I am thinking about getting a Worms game. I do not have much experience with this series, but I know it had its ups and downs.
Would you be so kind to suggest the one that would provide best experience in single player mode (the one with most missions/most challenging AI)?
Thank you in advance.

Pretty much so. Both WA and WWP have different mission types, and have completely different mission sets from each other. WWP also has the Forts mode, but WA's patched nature gives better gameplay.

Great, I think I will get WA. Thank you for advice genkiii and Plokite_Wolf.

I am late for an answer, but I would like to underline that the SP fun is mainly in the missions. Playing deathmatch against the CPU is hardly any fun, it is good only for training.

Missions instead have a fairly different game play, it's more like a puzzle game than a normal Worm game because you have different objectives and often different weapons than your adversaries.

Said all that, even the strangest puzzle hide in shame compared to play with few friends. Internet play works great, so you don't even need to have a friend nearby; you only need a skype session and a way to open a port in your firewall.