We only had two Source entries, and I already know what one comprises of, so I'm not even going to bother taking a look at them.
You don't have to judge them seperitly, you can do like it was done in snarkpit, and if I remember correctly the source entery got to the third place and the Hl1 first.
You just need to ignore the advantages of the source engine:
1. Graphics- things that are uniqe for Hl1 may not be uniqe for source. Like cool and real looking terrain, it's harder to create it in Hl1. Or a fake 3D skybox in Hl1, I hardly ever see anybody place things where you can't get to them and give a feeling that there is something beyond the tiny box of the level. In source however you can see in every respectible map a 3D skybox.
2. Originalty- Things that might be quite original in Hl1 may not be original at all in source. Like a ruined city thats not in the middle of the desert. In Hl1 it was done before but it is still a bit original, in source it's like copying the original game. Also if one is funny then it sould give it some extra points.
3. Gameplay- Nither of the games have a particular advantage in this field, it's just a matter of opinion. But if you can still know which one has gameplay or not and which is funner. If one has only action with no thinking it will be automaticly rated lower then a map with puzzles and thinking.