"Ti "shepherd's hook" stakes are nearly useless except in perfect soil conditions."
That's one opinion.
I've been using titanium shepherd's hook stakes for some years now, and I find that they are just about perfect for any soil that I've found in the Sierra Nevada or Alaska.
Yes, aluminum is lighter than titanium for a given volume. However, titanium is much stronger than aluminum, so when we are talking about something that must resist bending, I give the edge to titanium. I admit to pounding on all of them with various rocks, and they don't bend.
I also have v-shaped titanium stakes, Groundhogs, Easton stakes, and other kinds.