Tecnu Rash Relief Spray is an OTC homeopathic anti-itch medication that uses grindelia robusta and plantago major to stop itching and help promote healing.

Calagel is classified as a OTC topical drug and contains dyphenhydramine hydrochloride, benzethonium chloride, and zinc acetate to help stop itching, dry up your rash, and protect your skin. Calagel also contains menthol for instant cooling relief.

They are both effective and it is up to your personal preference as to which is better.

See:

Calagel drug facts

Tecnu Rash Relief drug facts