Hm, MC does seem pretty serious about Lucy.
But apart from the model I didn't notice any differences in the story (maybe because it skipped some Charlotte scenes).
I still think the story will play out pretty much the same for Emma, since the developer is probably too lazy to write separate uncle/father paths, so I will stay on the Lucy path for now.
If it ever changes I'll just pick what's best for Emma.
Luckily that's very easy with skipping and the low amount of choices.
There is definite changes when playing Lucy path or not.
******Spoilers********
So far there is maybe 3 paths:
1) Lucy Path (Locks you out of everything else)
2) Model Path (Not sure about this one yet, but because you must have rejected Lucy before, it locks you out of Lucy path)
3) Charlotte, Emma, Suzie path Locks you out of Model and Suzie path (since you needed to reject them both)
The dialogue with Lucy is very different weather you are on her path or not.
1) She openly calls you her BF and the MC confirms this.
2) At the Hotel you get some extra dialogue in her room (Kisses, but no sex)
3) In the park you get extra dialogue together with kisses (If I remember correctly)
4) You have no option to fool around with the model before the pool
5) When the model is at the swimming pool, she will act jealous.
6) MC tells her he wants her, but that they must wait before sex.
Model Path
1) You can flirt with her, before Charlotte
2) You can fool around before Swimming pool
3) Not sure if this route will exclude Charlotte but definitely excludes Lucy (Not possible if you did not reject Lucy)
3)Charlotte/Emma/Suzie
1)If you reject both Model and Lucy, you are probable on this path.
PS. I did not look at the code or WT, but I played different options for Lucy to notice the differences.