5.8m extended would do you for most jobs. However, it won't let you extend above a window over a bay on older, high ceilinged houses. I have used a 2 x 3.5m ladder (ext length 6.1m) and that sometimes only made it on a 3 rung overlap (I think you're meant to have 4 rung overlap).
So, for most purposes, OK. For the odd job, no.
Apart from that, maybe a short triple would be less stable than a longer double (just asking - not sure about the last bit).