and you can sometimes alter keys buttons - in cod 7 there was option press once to aim and no need to hold - then press again once to zoom out or normal hip fire
on games like bf4/3 i prefer hold as the click means you have to click off the sights which is very weird for me. Although if your playing arma 3 where you might be on a cheytac sniper rifle on sights for a good 10 minutes click is better.
Well, I just started playing bf3 and from my other previous fps game experiences, I just do much better with click because with hold, i'm putting extra pressure on the miuse and it messes up my aim slightly
Well you don't have to hold the click to hard a light press does the job train yourself to use hold on bf3 its much better as its faster to let go than click again and this will probably get you killed quite a bit when your in those fast paced 6 on 1 gun fights
I use click to toggle, partly because I am used to it and partly due to the Arma controls. Not sure how letting go is faster though, its a couple of mm either way.
Well using click is two actions and holding and letting go is one, hence why its faster its not needed on arma but when your on bf3 and your popping in and out the sights in close range shootout it makes a huge difference