Erector Set
Overall, Tamiya models "should" be somewhat sturdier than equivalent Erector Set models due to their thicker parts, and both "should" be sturdier than Lego Technic due to their physical fastenings rather than simple snap-fit, but both Erector Set and Lego Technic are much more flexible thanks to their complete lack of single-purpose part-joining points, self-tapping screws, and the need to glue parts.