As has been said earlier, when I get the R/T time, I will pass the reason for the vector and the relevant traffic to the pilot. More often than not, if I am vectoring I don't have time, and the only time I will pass traffic is when I want the aircraft involved to know about each other so as to adjust rates of climb and descent to try and avoid a superfluous RA.
Just a tip (especially to the Speedbird moron who flew into Abu Dhabi a while ago), if you are 6 NM behind and 30 Kts faster than the preceding traffic and you have 20 minutes to touchdown, yes you could get your nose in front at some point in your descent. BUT, I have a choice of slowing you and maybe giving you a little turn, and getting my ten (ie. an adjustment of 4 NM) and all the while being able to give unrestricted descent to both aircraft. The alternative (the preferred one for whinging "but we are faster than him, it's not fair" poms) is to restrict the following aircrafts descent, and push down the preceding traffic early, while I try and get the following traffic in front, then vector the crap and slam the brakes on the front aircraft, so I can get my ten (ie. an adjustment of 16 NM).
Bottom line, someone has to be number one and someone has to be number last. The world isn't out to get you if you are number last, and whether you understand why you are number last or not, you will still be number last. Moaning about where and why you are where you are in the sequence, will only succeed in you and your airline's fellow crew members, being number last all the more often.