I know one Sophia properly, my OHs niece, she's nearly 7. I also know of a girl I went to school with calling her daughter Sophia as well. Where I live it's mostly Isabelles, Isabellas and Graces...
I think it's a lovely name and personally I prefer the spelling Sofia, I think it's prettier written down. I lived in Spain for five years and only knew the name from there and when I moved back to England I thought it was weird written down with a -ph-!
Pronunciation-wise I pronounce both the same way. I think with a lot of names you'll get people saying it wrong and I wouldn't base my choice on other people. My son is called Caleb and my sister in law still can't spell it after two and a half years and I have to correct people on it all the time, but I love the name and that's what matters!