Don't know if many people know this but vikan flocked brushes come in 3 different grades- soft, medium & hard.
I use a vikan rectangular medium-flocked, rectangular monofilament & a rectangular soft.
The medium flocked is a great all-rounder especially for regular maintainence cleans, the soft flocked is perfect for thin, old glass, leaded or georgian & the mono' is good for first cleans, minging cleans, regular & con' roofs. Each of these brushes cut right into the corners, have good flow through & perfect results are acheived without cleaning the top frame.
The stock (black plastic) of these brushes is quite bulky mind so to make them better you can grind/shave all the excess plastic stock away to leave only what is nessesary to hold the bristles in & the whole thing together. this makes them more user friendly ( & a wee bit lighter for the wimps).
I have used gaz swivel (salmon) utter tripe, unger- not bad, vikan oval (old type) not very good, facelift- good on bigger glass but too bulky for most domestic, another salmon- again utter tripe.
It's down to personal choice & wfp technique at the end of the day. the modified vikan rectangular with a MKII swivel work perfectly for me, day in, day out.
tony