If I may offer my definitions, a smile is produced when the corners of the mouth are drawn upward by the corresponding facial muscles, while laughter is produced when your vocal chords come into play. A smile is a sort of weaker reaction to a funny event, thing or statement - as in a joke - while laughter is a much stronger reaction to the same. Smiles have intensities, as do laughter. A smile can be anything from a one-sided smirk to a full blown grin. Laughter can manifest as a tiny "tee-hee-hee to a full blasting guffaw. And yes, they are two different things, or reactions, entirely. And their effects are also different.
If one were to slip and fall to the ground, helped up to your feet by a smiling Samaritan, one would probably smile in acknowledgement or to oneself for being clumsy. But if a nearby bystander bursts into laughter, I don't think you would respond in kind, but with something more unpleasant. If one were a stand-up comedian and after delivering a night of jokes, you only see the audience smiling, then it may be time to start a new career. But if the audience suddenly bursts into boisterous laughter, with some coughing and in tears, then you know you will go far. Smiling and laughing are indeed two different things, I agree. But there are situations when a smile alone is as bad as laughter.
If a doctor smiles while attending to your daughter who has just been struck by a speeding car, how would you feel? He isn't laughing, just smiling. How do the relatives of all those who disappeared during the Marcos regime feel when they see a portrait of him smiling? He's not laughing, just smiling. How do all those scammed by Manuel Amalilio feel when they see him smiling on television? He's not laughing, just smiling.
Humans have probably the most complex set of emotions, where a smile can be both pleasant and unpleasant, just like a tear can be for joy or sorrow. The context or situations in which these emotions come out play a part in their ultimate meaning. Normally, a smile appears in times of happiness, stress-free situations and total well-being. It is a feel good emotion, generally speaking. But in another world it could mean cynicism, sarcasm, insult. We would do well to check when our emotions are appropriate, or inappropriate.
As for me, I just can't help but smile.