C_N,
As it is mentioned above RFE does not mean rejection but validation of application. It is very common to get RFE about employer-employee relation if your petitioner and your client you deliver service are different. Since it is said that your client already provided you a client letter things should be easier ( most of the times client does not provide such documentations to contractors). As you said your employer is positive to respond RFE there is nothing to worry about. If your employer is shady consultancy then the chance of responding RFE is less (I have experienced that my employer lied in the past about responding RFE when they had to provide info related to their company).
Other than that I do not see any problem going for PP. If you have everything that you can provide that are asked on RFE there is no reason to not go for PP. If there is not enough evidence to support RFE, petition will be denied either it is P P or not and same is true other way around. If I were you I would go for PP and get the result soon that would provide me enough time to prepare myself rather than tracking my case everyday at uscis.org. The only advantage for not going for PP is saving that $1225 here.

P.S: Above is not a legal advice, just my opinion.