I own a Ford F150 Platinum. It's not made of Platinum.
I own multiple Titanium (Citizen) watches and love them. I swim with them regularly and they look like new (minus the scratched crystal from my abusive lifestyle.)
I see a huge mistake coming here for Apple... Not making a titanium edition/case.
Comparing Titanium with Stainless Steel when used inside the body:
Medical grades of titanium have a significantly higher strength to weight ratio than stainless steel. Titanium implants are light, weighing about 45% of comparably sized 316L stainless steel implants and yet the single load strength of Grade 4 Pure titanium is only about 10% less than that of stainless steel. Titanium alloys have higher tensile and yield strengths than stainless steel. With internal fixation, the resistance to repeated loads (cycling) is much more important than the ultimate failure strength of the implant. Compared to stainless steel, titanium has superior strength under the high cycle repeated load stresses encountered clinically with internal fixation. Titanium and titanium alloys are not notch sensitive, which means that stress raisers have minimal effects on mechanical properties of titanium implants. Titanium has a lower (approximately 50% less) modulus of elasticity than stainless steel. A lower modulus of elasticity means that titanium is significantly less stiff than steel, which helps to minimize stress shielding of bone. Compared to bone, titanium is approximately 4-5 times stiffer and stainless steel is approximately 10 times stiffer. Titanium is immune to fretting and local corrosion that is seen with stainless steel implants. Titanium implants demonstrate negligible magnetism and causes less interference than stainless steel when scanned with Magnetic Resonance Imaging (MRI) equipment.