I believe someone else already pointed out the Kadet Senior is a 3-channel, the LT-40 is a 4-channel and will fly on a .40, which is a small, inexpensive engine. A 3-channel radio can be had with somewhat less expense, if you wish to go that way.

If you wish to build, either kit is fine. If your primary interest is flying, the LT-40 is available in ARF, which requires less building. Again, either is quite adequate as an introduction to RC flying, especially if you have a good instructor.

If your plans include building big models, start with a kit. If your interest is mainly flying, an ARF is quite adequate. Personally, I advise students to start with a flight simulator, to see the difference between 3 and 4 channels. Then, if the desire to build exceeds the desire to fly, buy a kit. If, with the simulator, you find the 4th channel desirable, start with the best computer radio you can afford, and a 4-channel plane.

Welcome aboard!
Dave Olson