I had a Concerto II S, 72 basses which I think is similar, just a narrower keyboard maybe? It was a good solid instrument, and I liked the tone. But I found for me it was neither one thing nor another - it was too big and heavy (for me) to play outdoors for folk dancing, but at the same time it was limited to just musette/not musette registers - so for performances when I'm indoors sat on a stool and weight doesn't matter so much it was a bit lacking. I sold it and now have a Weltmeister 48 whichi I use for outdoors 'strolling', and a Concerto IIIN for playing indoors, evenings in pubs, etc. Compared to the IIN it has a extra bass register in both bass and treble sides, which adds quite a lot to the sound.
NB: I've only been playing accordion for a year, so my opinions are only those of a beginner!