If you want to choose which name to call yourself when you meet English speakers, I'd go for the second one: Olga Simonova.

We are all familiar with the Russian name Olga: it won't cause any problems, whereas the less familiar Olya might be harder for English speakers to hear. English speakers might also struggle more with the consonant cluster 'osla' than with the simpler 'ova'.

'Olga Simonova' sounds nice: a very typical Russian name which westerners should have little trouble either saying or spelling.

They all sound pretty. The assonance of the "o" sound and the rhythm of the syllables is nice.

As others have said, if you say "Olga Simonova" many English speakers will guess the correct spelling just from the sound. They may ask you to spell it out, to be sure, but it is what they will expect. For the others, you will need to be careful and put extra emphasis on the "surprising" letters.

"Could you spell that, please?"

"oh, ell, WHYYY, a; ess, eye, oh, en, oh, ESSSSS, ELLLLL, a."

All of them sound "Russian." Although I know people named Olga who are not Russian, we think of it as a typically Russian name, and the "-ova" ending sounds very Russian, too.

As others have said, "Olga" is well-known. To my ear, "Olya" is a little softer and prettier.

Ольга Симонова sounds very typically Russian. I've been hearing Russian names since I was quite young, so it sounds natural and nice to me Дарья, Наталья, Ксения and Светлана are a few other female names that are typically Russian. On the other hand, names such as Анастасия and Александра are of Greek origin.

I agree with Su.Ki., especially that the osla part is harder to say. I also agree that Olya is more unusual and you’d have to put up with people not hearing it quite right. You’d need to spell it for anyone that needed to write it down for some reason. That said, I think it sounds nicer and more interesting.