your gonna get a lot of different answers as brushes are a personal choice.i have loads(mostly gardiners)
xtreme
supreme
ultimate
supalite
sill
xline
in most types.flocked,mono,stiff,hybrid bristle etc.
in fact ive got that many i wont need to buy any for at least a few years!
my main brushes for lots of maintenance window cleaning at the moment are the ultimate medium mixed,the xline mono and flocked versions depending on type of windows(leaded etc) and frequency.
sill brushes or xtremes for f/s/g cleans and conservatory roofs.
supreme soft for washing the van/car.
IMO the supalites and xline brushes are the most hard wearing but can seem a tad heavy compared to the ultimates/xtremes.
in future i think ill stick to buying the ultimates and xlines and maybe the odd sill radius brush.these are fantastic brushes and i dont need any others TBH.