OP- I always clutch down and rev match every gear on ever stop sign, stop light, slowing down or what ever other kind of stoping and slowing... it dosen't matter, i use the bike in its optimum operational and proper manner, also matching the front and rear breaking with the down shifthing. everyone has their own style, and depending on what type of bike, one may be comfortable using either one of the techniques, but from experience, the "proper" format for down shifting is rev-matching every gear down with moving :mass" speed vs transmission "gear" speed & engine "piston" speed. you don't see gp1 bikes pulling the clutch in slowing down to a corner or turn. Not saying you must operate a bike this way, just telling you what is the absolute optimal way to operate a bike or even a car or anything mechanical in that matter.
advantage of downshifting every gear, like others mentioned:
.you will be able to move of the way for an emergency
.your brain will memorize so well to rev match, and subconsiously automatically recognize transmission speed vs engine and moving speeds and down shifting every gear, the noises and overall make you a very confident, cool headed and calm rider.
. When your brain is so realaxed and the body is doing all this as second nature your mind has more time and space to think of and react to other things.
. i bet riders who clutch in and just roll to a stop or try to fidle with the gear after, either, must come to their slowing speed before their habbit of downshifting or selecting proper gear or releasing the clutch to match speed, while sometimes have trouble with the flow of traffic, delaying cars behind leaving gaps infront of them, getting of a green light too slow that turn green when their actually slowing down when their still rolling clutch in too fast to engage in 1 or 2, or too slow for engaging in 2 etc.
what would you do if you're slowing down, clutch in till you stop or engage it in 1st or 2nd but before that your breaks fail? downshifting every gear makes your right foot and figers keep tabs on the working/functioning of the breaks at every stopping second from start of its life, no surprises, and theres so much more benificial to useing this style of downshifting then not.
to me not down shifting and rev matching every gear is risky, and leaving more chances for things to happen that need not be like the question "should i or should i shift this way or not" the best and safest rider is one who is confident in the control of his/her machine at ALL times and has no doubt about it.
I wouldn't take chances me or my machine.