Is there a pronunciation difference in [name_f]Emilia[/name_f] vs [name_f]Amelia[/name_f]?
Pros or cons to using each?
Which do you prefer?
I pronounce them with the slightest difference that I’m not even sure can be heard to be honest. I say eh-milia and ah-milia.
I prefer the look of [name_f]Emilia[/name_f].
Lastly, I always compare nicknames…
While most in this case are the same…[name_f]Millie[/name_f], [name_f]Mia[/name_f], [name_f]Lia[/name_f]. [name_f]Amelia[/name_f] gives you options like [name_f]Amy[/name_f] and [name_u]Mel[/name_u] while [name_f]Emilia[/name_f] gives you [name_f]Emmy[/name_f]
Me and my other half were having this debate the other day, my worry with [name_f]Emilia[/name_f] is that people would assume it was [name_f]Amelia[/name_f] and she would spend her life correcting people as they do sound so incredibly similar and for that reason alone it put me off. The other thing to consider is that shortened down they give potentially very different nicknames; ‘[name_f]Amy[/name_f]’ or ‘[name_f]Em[/name_f]’ However it could just be ‘[name_f]Lia[/name_f]’…
I do pronounce them differently: “Eh-mee-lia” versus “Uh-mee-lia,” but it’s subtle in my ([name_u]West[/name_u] Coast US) accent. I like [name_f]Amelia[/name_f] better as a full name, it looks a little nicer to me written down, and it sounds a little more spunky to me (maybe because I think of [name_f]Amelia[/name_f] [name_f]Earhart[/name_f]?), and I would also worry about [name_f]Emilia[/name_f] being always mistaken for [name_f]Amelia[/name_f].
But I do like [name_f]Emilia[/name_f] as well. It seems more international in its pronunciation ([name_f]Emilia[/name_f] is pretty much the same in English and the romance languages, except the E becomes more “ay” than “eh”) and has the added bonus of the adorable (and fashionable, right now) nickname [name_f]Emi[/name_f]/[name_f]Emmy[/name_f].
ETA short version: [name_f]Amelia[/name_f] if you plan to use the full name, [name_f]Emilia[/name_f] if you want to use the nickname [name_f]Emmy[/name_f].
I would basically say them both pretty much the same way, to be honest. Forgive my ignorance, but to me they’re the exact same name, but with different spellings.
I prefer [name_f]Amelia[/name_f], myself. I think it’s more aesthetically pleasing 
I agree with @relica, I don’t pronounce it with a difference that generally sound too different. I prefer [name_f]Amelia[/name_f] because I associate [name_f]Emilia[/name_f] too closely and similarly with [name_m]Emilio[/name_m].