Well, I cant suggest much, its up to you to decide after you check all pros and cons. If it wont cost you additional money you probably should go for Xperia S, otherwise its better to look at newer Sony Xperias V or T. Or try another brand.
You shouldn't worry much about yellow tint problem it was a serious problem only in first shipments of Xperia S (you should check the production week under its back cover, look for 12Wxx sign, there "xx" is a week of production, after week 16th its pretty safe to purchase). However you should still notice some little yellow shade on display in general, cause compared to Xperia P - Xperia S doesn't have "White magic" display technology and its white is not as good as on Xperia P.
The camera on Xperia S is a major problem for me, I dont know the quality of camera on Xperia P, but Xperia S has a really bad one. The low light poor images and focus problems you heard of are all true, Sony has made a complete failure in that department.
