No one size fits all
With the differences between new trials riders one size is unlikely to fit all, especially when one size = 125. People sure seem to have lots of passion about what new people that they don't know should ride... I picked up a late 90's 270 gasgas and it seems fine to me although I'm 6'2"/215 and ride dirt bikes already (and mountain bikes forever).
On a different note playing around on the trials bike in my 1 acre backyard is tons of fun and doesn't annoy the neighbors or my wife. Wish I would have tried it sooner...
02 E440 St legal Cannondale
98 gasgas 200 enduro
97 gasgas trials