Hola Jordan 

They are often interchangeable as  both are structures that express an action in progress but ir + pres. participle is used more for something that implies some sort cumulative action, like a bit by bit progress. For example: "Pronto te irás enamorando de esta bella ciudad." - Here, for example, it wouldn´t sound right to say ""Pronto te andarás enamorando de esta bella ciudad." because "andar" doesn´t necessarily have that nuance of bit by bit. 

Also, andar + pres. participle is often used either in the present tense or the imperfect (ando ...., andaba...) more than other tenses like perfect tenses, while ir + pres.participle is used more widely in all tenses. 

Saludos cordiales