The I&T manuals are more "overviews" of your equipment. The WSM is specific to the B5100/6100/7100 family that your tractor belongs to and is
much more comprehensive. I have a feeling that if you purchase the I&T manual you will likely purchase the WSM later anyway because you may find it lacking...
Something to consider - a good set of manuals (service manual and operator's manual) may cost you $150-200. You will certainly get use out of them and when you sell the tractor the new owner will gladly pay that amount to receive those manuals. If you look at it that way, they do not really cost you a lot. We really encourage every Kubota owner to obtain as much reference literature they can about their equipment (parts, service and operator's manuals). If you are not sure where to find them - Vic can obtain them for you as well. If you get all three he might be able to toss a deal in for you (Vic: wink wink nudge).