I'm pretty sure everything in HL1 has more health too. Especially the soldiers. The combine soldiers in HL2 can be downed with one well placed right trigger shot from the shotgun. I don't think the same is true for the HL1 HECU.
In Half Life 1, when playing on hard, being within a couple feet of a grenade launcher blast would kill you. In Half Life 2, even on hard, none of the soldiers even launch a grenade.
I have two questions: 1. Did anyone else notice this change in difficulty? 2. Why is HL1 so much more difficult?