Jimmy Shand ruined piano accordions for me; I don't really like the look or the sound. I'm thinking strictly buttons!

I suppose the real question is, if I wanted to produce a sound something like John Kelly's Polly Vaughan or Dick Miles's Willie o Winsbury (i.e. mostly chords, with the voice carrying the melody), are there good reasons for going for a melodeon rather than a concertina?

("Something like" is intentionally vague - I realise that John's playing harmonium on that song.)