Very good question Daz, I been thinking the same myself only yesterday. I remember years ago a mate of mine had this huge bass scrapping really well on a Toothy Critter shad, this bass was like 9lb or something, as he got it near him the line snapped (14lb Fire Line) and the reason boiled down to him not using a clip, he had tied direct and there was paint in the eyelet and the sharpness of the paint parted the line. Ever since seeing that I have insisted on using clips, but recently I have thought that most of the jigheads I use do not have paint on them........ I dont think you need a clip unless you know you are going to be changing fairly often, and even then its not that important is it.
ive heard it somewhere ****, on youtube i think....an american chap talking about rigging sp`s,he states you should always tie fc straight on to the eye as tight as possible so the line stays running upwards with the eye of the hook to give better response,makes sense than havin a slack clip.
Personally i like to use a clip, it's not as direct but with fairly stiff flouro I like the hinging effect, just think it gives it the freedom to behave a bit more naturally on the drop.
My two pence :-D