Picante vs. especiado vs. picoso
The Spanish language has several words to describe the concept of 'spicy', namely 'picante', 'especiado', and 'picoso'. Although they all deal with some aspect of the idea of spice or heat, there are subtle differences among them.
Picante
In Spanish, 'picante' is generally used to refer to any type of food that has a spicy or hot flavor. It can be anything from a mildly spicy dish to a fiercely hot one.
Ese chile es muy picante.
(That chili is very hot.)
La salsa de tomate es un poco picante.
(The tomato sauce is a little spicy.)
Especiado
'Especiado' refers to a dish that is richly flavored with spices. While it may also imply that the food is hot or spicy, its main connotation is that the food is full of diverse spices and robust flavors.
El curry es un plato muy especiado.
(Curry is a highly spiced dish.)
Este vino tiene un sabor especiado.
(This wine has a spiced flavor.)
Picoso
'Picoso' is commonly used in Mexico as a synonym for 'picante', meaning it is often used to denote food that tingles or burns the tongue. It carries the connotation of being peppery or tangy.
La salsa verde es muy picosa.
(The green sauce is very spicy.)
Los jalapeños son muy picosos.
(Jalapenos are very hot.)
Summary
In sum, while 'picante' and 'picoso' primarily convey the sense of heat, or bite in food (with 'picoso' more commonly used in Mexico), 'especiado' focuses on the rich presence of various spices leading to robust flavors irrespective of heat.