To answer the original question: No, I don't feel guilty whether it's RnT or FS. Having said that, I prefer RnT over FS only because I get a little paranoid about disease even with using protection.

The difference between sex for money and sex for free, is that sex for free costs a hell of a lot more. Having had committed partners, as well as a number of mistresses over the years, and frequented strip clubs, massage parlours and private operators, I can categorically state that use of professionals costs a shit load less in terms of money, stress, guilt, demands from all parties and the emotional fall-out when it all goes fucking pear-shaped.