I own one 4 piece 6 weight rod and the other 5 rods are all 2 piece. My personal preference is a 2 piece rod. I just like them better. I do not feel, with a quality rod, that there is any difference in the rod action between 2 piece and multi-piece rods. If I should live long enough to actually retire and have enough income to do any traveling to fly fish, I will probably own more multi-piece rods. As it is now, my fly fishing is limited to here at home with 2 rivers and 4 lakes within 20 miles of my home.
Whether 2 piece or multi-piece is for you will need to be your choice. There are just as many pros and cons for both, so, you do what best fits you. Somewhere down the road you will own many more rods! I am sorry that the salesman that you had did not know more about customer service.
Warren
Fly fishing and fly tying are two things that I do, and when I am doing them, they are the only 2 things I think about. They clear my mind.