SDL vs. Allegro

That's like asking "Which is better Coca Cola or Pepsi?" It's just an opinion.

It depends on what you want to do.

Define "better".

Personally, I'd say SDL in any case.. :p SDL is great really.. I'm sure not everyone will agree with me though..

Basically, SDL and Allegro do almost the same thing, just differently.

In my opinion, Allegro is easier to use if you're just getting started in 2D. Everything is laid out for you in an easy fashion with Allegro, and you probably won't require any extensions to get started. One thing Allegro has over SDL is the ability to draw most primitives by default without having to write you're own functions. Although, you could just get SDL_gfx and have the same effect. Overall, Allegro is easier to learn, so if you've never done any 2D programming, I'd give it a try.

SDL may not be as easy to learn, but I believe it is more capable than Allegro (after you get all the SDL extensions). The greatest thing about SDL, IMO, is all the great extension libraries to it. Things such as SDL_mixer and SDL_net provide greater capabilites when making 2D than Allegro can offer. However, I found SDL to be generally harder to use than Allegro.

Overall, both are great 2D libraries, so it is up to you to decide.

IF you're interested in 3D games, SDL also works well with OpenGL.

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That is wrong on so many levels, and why alegro looses.

No vs. threads, please. They accomplish nothing. Do some research and decide for yourself.