[towaway1138]

If you're generating nodes in an abstract graph (e.g., moves in chess), iterative deepening can be incredibly space-efficient, whereas BFS can rapidly consume an exponential amount of space.

As you point out, IDFS (or IDA*, etc) work far better if you have a means to avoid re-exploring the same nodes repeatedly.

Nonetheless, run-time can theoretically be greater, since you're iterating. Theoretically, though, each iteration will take N times longer than the prior, which means that the running time up to the final iteration doesn't matter that much (because it's such a small fraction of the total). The extra bookkeeping required by BFS can easily outmatch that in running time.

Definitely, it all depends.