Ambas se pronuncian idéntico (lle), lo que pasa es que hay culturas como la ecuatoriana en las que la pronuncian como una i; pero en realidad el sonido debe ser idéntico en ambas, no te dejes confundir por los que la pronuncian mal.

https://www.youtube.com/watch?v=kFpimuSe_1c

Hi!

In Spain Y and I have the same pronuntiation. 

Y/I and LL have a slightly different pronuntiation but most of people pronunce LL like I/Y.

But in some parts in Spain LL is pronunced differently from I/Y.

Writing about pronuntiation is quite different but you can use online dictionaries that read you the word and you will listen to this words and the difference.

They are different but Spanish language has not this problem, if you speak with someone from Madrid you will listen always Yuvia, from Buenos Aires the sound will be ssshhuvia, if you are able to pronun "LL" it will sound like     L i u v i a, where first "i" is so closed to "L"

But if you want to pronoun perfect it is so easy

LL    move the tongue to the palate

Y     move the palate to the tongue

and be carefull about not atack hard, stopping air and making one explosión ( CH )

Fácil!!!!!!

the sound of "ll" is like a the final part of will ('ll),

but the "y" has 2 sound example:

when the "y" is between 2 word ex: Ana y maria, casa y auto, reloj y zapato, etc. the sound is like a vowel "e".

the second sound is when the "y" is inside of the word, ex: yerno, ayer, ayuda, etc. the sound is like a the first wowel of yesterday.

then we also use the "y" in the final part of the word (the words with "y" in final part are almost dificult that you hear)ex: freddy, hay, caray, etc. he sound is like a the vowel "e".

sorry for my write, but I'm not good with the english.