They are words that have come to English via different routes. "Deceiving" is the present participle of "to deceive", with the earliest common ancestor being the Latin noun decipio. The passive past participle of this noun in Latin is "deceptum", and on this form it is common to derive an adjective with a postfix "-ivus", hence "deceptivus". This word then enters English in a parallel manner, giving "deceptive".

In this case they have identical meaning in context, but there's frequently unpredictable semantic drift in these pairs, if both do end up in English.