For feel, one should expect a smooth feel from the flats. There will be much less screech when you move around the fret board. There are different gauge strings also that will affect the feel of the strings. A heavy guage will probrably take more time to become comfortable with than a thin guage. The feel of the round wound is courser and more noticable under the fingers in the begining with the same rule of the guage affecting the feel.
As for sound or tone of the round wound, there is a considerable difference in tone compared to flats. James Jamerson used flats on all the Motown songs wich you can listen to yourself. Most of the early music used flatwond because there were no rounds to use. Im not sure when rounds were introduced but they became quickly popular because they are snappier compared to the flats. Hope this helps.
