Pronunciation and regional differences on this topic

Question

Thank you for adding this topic. I'd like to make 2 suggestions.

First, is there a regional preference for using the two pairs of interchangeable words? My understanding is that in Latin America, people tend to use aca' and alla' whereas in Spain, people tend to use aqui' and alli'. Is this correct?

Second, I am not sure whether the pronunciation of ahi' and alli' are the same. Since "h" is silent and "ll" has the "y" sound, I suppose they sound differently, but the sounds /i/ and /yi/ really do not have much noticeable difference. Is there a way to practice distinguishing the two or we can more or less treat them as sounding the same? Thank you!

Answer

Hola Michael
Thanks for your comment. 
Yes, we can say that "acá" and "allá" are definitely more present in Latin America, however, they do use aquí and allí as well. 
It is in Spain that the use of acá and allá are a lot more limited to specific contexts. You may hear "acá" in certain set phrases:
¡Niño, ven acá!
Come here boy!
And allá is also used in Spain with the idea of something that is very unreacheable:
Allá en esas tierras lejanas...
Far away in those distant lands...
As for the pronunciation of ahí and allí, yes, you're right. It's really unnoticeable for a non-native. As the yeísmo is so extended in Spain and Latin America, and the "ll" is pronounced as "y" which has a very soft sound, this makes it really difficult to differentiate those two. 
When you pronounce ahí, bear in mind that you go straight from a to í: [aí] 
If you try to say this: "ah ee" you got it.
When you pronounce allí you have that [y] sound in the middle: 
so you say "ah yee"
Not sure this will make it clearer as it is so difficult to explain without being face to face...
I hope it shows some light...
Inma