To be broad, it's mainly how the social behaviour manifests that separate the two, and I suppose how severe the desire for routine/structure affects the person.
Generally, people born with AS usually end up as odd and eccentric or overly formal and pedantic as adults, with a clear overt attempt to fit it (even if they didn't as children), whereas those with AD appear uninterested in social and emotional connections (which is thought mainly due to the greater difficulty in social interaction in the latter disorder nowadays). However, the latter, if high functioning enough, usually form a bond or two with those close to them (a carer for example). In clinical and mechanical settings, the higher functioning people with AD will appear indistinguishable to those with AS for the most part.
Speech delay also means understanding speech, not just speaking; there's receptive and expressive speech, and both are affected (though to differing amounts).