ISIS and al Qaeda may share a common enemy, but terrorist experts say the two groups’ fundamental differences have led to a competition between the two for recruits.

Terrorism and security expert John Thompson says both groups have a shared goal of establishing a caliphate, or a united, global Islamic theocracy. But because of their different tactics, they are recruiting different followers.

Al Qaeda is a more established, disciplined group than ISIS, and also much more observant on theological issues, Thompson says. ISIS is less concerned with the finer points of ideology and more focused on leading an immediate revolution.

“They’re very aggressive, in your face and they want it all now,” Thompson told CTV’s Canada AM Thursday.

To potential followers, ISIS can offer angry young radicals the promise of immediate, brutal attacks, sex slaves, concubines and looted goods.

Al Qaeda, on the other hand, offers none of that because they are more methodical in their approach, choosing their targets carefully. That might make them seem comparatively boring, Thomson said.

“Al Qaeda is a bummer,” he said. “You join up and have to learn a lot of ideology and discipline yourself and wait. With ISIS, you get to go and humiliate people, kill them, and if they don’t marry you to somebody, you can grab a sex slave.”

ISIS is also doing a better job than al Qaeda of recruiting young followers through social media, and are more visible right now because of their high-profile attacks.

But Thompson says ISIS is also impatient and more careless in their operational security. Because of that, they have had less success with plans for attacks.

For those reasons and more, Thompson suspects al Qaeda poses the longer-term threat.

“ISIS is more of a threat right now. They’re the only group that has grabbed territory and they’re being a lot more aggressive. But when ISIS is finally quashed, al Qaeda will still be there,” he said.