Prefab or traditional granny flat in this cost crisis

basically seeking opinions given rising costs. we have plans approved for a 30msq granny flat. got quotes for more traditional construction for around 80-100 ballpa k but will need to get building drawings, engineering etc done which will all take time. To go via prefab will be around 110 roughly but will be much faster and I'm guessing have much less variables that could blow out cost wise such as no concrete slab etc. all things being even we'd prefer the traditional slab method so it's on the ground for elderly visitors and more choice in finishes etc but given the global climate wondering if you'd just pull the plug now on the confirmed quote for the prefab rather than the more uncertain ground up. interested in people's opinions about the choice. thanks