Why do most radio restorers use orange drop capacitors as oppose to other ceramic type caps? Thanks!?

If you're restoring an old radio, you want to use parts that look like the original parts. Part of the joy of an old radio is beauty of the construction.

Orange drop caps use a plastic film dielectric.

Ceramic caps, especially high-k (X7R, Z5U, ...), are microphonic (act like a microphone) which can cause issues in audio amplifiers. High-k ceramic caps change capacitance value with applied voltage making them unsuitable for filter stages and areas where minimizing distortion is important. High-k ceramic capacitors have a pretty bad temperature coefficient, so the value will change with temp making them unsuitable for certain types of circuits.

Plastic film caps don't have the problems of ceramic capacitors. However, there are types of ceramic capacitors that are stable, aren't voltage sensitive, and not microphonic (NPO or COG type capacitors).

The color is just the color of the epoxy used to coat the parts. Bright colored orange was associated with Sprague back in the day.

These days, for printed circuit board mounting, I favor Wima capacitors since they are in a rectangular case.

It called titanium capacitor was invent in the 70', small in size with larger capacitance than ceramic type. It was up to the designer's choice to choose the parts that fit the board size and cost. No special reason, also less existed in circuit nowadays because it has too low voltage tolerance.