I would say TMI is much more technical because it's written for the "Hardcore Dharma" community which is far more technique-oriented than Goenka. Goenka doesn't approach the stages of insight adaptively, which can easily frustrate practitioners of mindfulness whose first intro to meditation is body-scanning. I would rank body-scanning as one of the least efficacious techniques with very poor results when applied to the physical pain that often results from long sits.

Good meditation teaching is equipping the practitioner with a toolset with the right tool applied for the appropriate stage of practice.

TMI and Mastering the Core Teachings of the Buddha are necessarily complex because they are treating the entire path toward nibbana as a segmented map of attainment. I can think of virtually no technique which can be applied from the beginning to the end except for very difficult-to-approach techniques such as shikantaza ("just sitting") or the ekayana ("one vehicle") techniques of the Quanzhen ("complete reality") Chinese Buddhism schools. If you think TMI is obtuse try and approach the Shurangama Sutra which is really a mindfuck. But here's the thing: unconditioned existence is a mindfuck so we often need "lesser" graduated techniques to approach the paradoxical nature of reality.

TMI does do a good job of not providing difficult techniques, but the I think Goenka explains watching the breath much more simply and better. He emphasises not grasping or being averse to what arises, and only working with your reality in that moment instead of wishing for things to be different. TMI does mention some of those points but I found the way Goenka reemphasised them to be very helpful