I voted for the MLRS turrets, because they kick ass. But actually I build blobs of 5 basic, 5 mlrs, 5 missile and 5 laser turrets (mk I until I have used them all, then mk II etc), combined with tractor beams (mk II and III preferably) and a few lightning turrets (mk III if I can afford it) and heavy beams (all marks).
And I have found a very effective way of distracting the ai on my home world: It seems that no matter what other kinds of targets are available, the ai always goes after the ion cannons. So first time the trader comes around I buy an ion cannon, put it somewhere far away from everything, and protect it with turret blobs and heavies and some mk I movable ships, plus several lines of tractor beams on his approach path. So, when the enemy arrives, he ignores everything else and goes straight for the ion cannon. Which has a lot of health and can sustain quite a lot of punishment. Of course I loose a cannon from time to time, but I am pretty sure that in those situations I would have lost my home command station instead, if it wasn't for the ion cannon.
Combined with spiders this even works reasonably well against aoe-immune frigates (which btw is a pita, enemy frigates has become a nuisance rather than a challenge after this nerf/boost - it is no problem to stop them, but taking them out has become a major pain).