Hi
Depends entirely on the smallest thing you intend to turn unless you already have an alternate means.
My most used Stebcentre is the 1/2" one which I will use on spindles up to about 2". From 2" - 3" I use a 7/8" and for anything larger I use a chuck.
To be honest, I could do without the 7/8" but not the 1/2".
Regards Mick