Well, I won't contradict GUEST (Robin) ... but then I also have G/C and D/G Anglos ... and a set od Bb/F reeds that will (one day) get into another Anglo body that I should be restoring ... and a Lachenal English I should also be restoring!
Many prior years of playing button accordion and mouthorgan predispose me to Anglo ... as well as the fact that this was the most common "folk" concertina - but my first concertina was a Lachenal in Wheatstone duet tuning. I know very well that all the duet systems can play wonderful music ... but I despaired of my ever doing so, after I heard what ~ 80-year-old retired Salvation Army Officers could do with them!
Concertina repairers/resellers suggest that the "sleeper" of the duet world is the MacCann (or it's earlier form, the Wheatstone Duet) ... that is, it's the system in which you will buy the most capabilty for the least price. Richard Evans, who repairs concertinas in the Blue Mts, behind Sydney, makes new Anglos ... but plays a MacCann.
I guess it all comes down to what you want to do ... and in what key. The MacCann is fully chromatic, but does favour some keys - obviously starting with those nearest to C major. I should ask Richard which keys work best on the MacCann!.