Elena is pretty bland and unmemorable to me; it's just not very distinctive. I like
Helena much better; somehow the 'H' gives it a lot more character and stateliness.
That said, when I see
Helena written down, my brain toggles indecisively between two possible pronunciations: HEL-eh-na and he-LAY-na. As a kid I always just assumed the name had the first pronunciation. Nowadays I'd be at least as likely to guess the second pronunciation instead. I like both pronunciations. A tiny part of my brain would also wonder whether the 'H' was even pronounced.