Chrome tape has the same reflective properties of any metal in that it reflects infrared (ie heat) as well as light. This can create those infamous hot spots which can damage plants. Mylar scatters heat, so it's better in that respect.

One thing to note though: mylar is not quite as reflective as many people will tell you, it's really only about 90% reflective, not 98 or 99%. Still, it's the most reflective stuff out there.

Spray adhesive, which you can spray from a can, works great for attaching mylar to flat surfaces.