I wrote the following article about the two exams. You might want to take a look at it:
As to your questions about the employer... it depends on the employer. Some employers will not pay attention to certifications at all. For them, it obviously doesn't matter which you take. For others, they will see that you have an Oracle certification, but have no idea what the exams mean. In that case, it makes little difference. However, I'll note that 047 comes with a separate certificate, so you would have both the Developer certification and the SQL Expert certification. They still likely won't know what they mean, but will see two certifications rather than one.
Then there are employers that know what the certifications mean (I'm one of those). If I interview someone that has the SQL Expert certification on their resume, I'm likely to ask them some complex questions about SQL. Based on their responses, I'll decide if I think they got the certification honestly or possibly with the help of brain dumps. If the latter, I'll probably toss their resume in the trash. In that case, having the SQL Expert on your resume could well be a negative -- even if you gained it honestly, but more through luck and good guessing rather than knowledge.
In fact I interviewed someone recently that indicated on their resume that they had experience writing complex code. During the interview, they could not provide any substantiation of that. This became a big negative -- not so much because I felt they could not write code as because I felt they were exaggerating their abilities. I want someone that I can trust to tell me exactly what they are capable of.