I thought filter holder type like Cokin is more versatile, especially for graduated ND filters where you can shift the filter up and down, also just by using different adaptor rings it can fit possibly all your lens, the down side is that it is a bit more bulky then screw-in ones.
If you have an assorted series of lenses, with different thread sizes, then it make more sense to get a filter holder. Just get the appropriate adapter and effectively, for each filter that you purchase, it fits into all your lenses.
filter holder pros
1) can stack filters without worry
2) can shift horizon of gnd up and down, not limited like screw in filter
3) you just need ONE set of filters, not like screw in, if your lenses all got different diameter then damn sian
4) much much much much lighter
filter holder cons
1) damn sian to screw on
2) cokin is a tad tad teeny weeny flimsy, but so far no problems or major accidents
3) easy to get your filters dirty lor. so must clean
for screw in pros and cons, just 举一反三 yourself :bsmilie:
for personal preference, i prefer the r72 screw in filter from hoya, mainly because of the amount of light let through and results. i've seen cokin p007 before, it is still ir, but somehow i don't like the colors. not exactly the same, and not so contrasty, i think
I'm not sure but at least for a gnd, it must be a filter type. pointless for a screw on. For the rest, the filter type just have one single majot advantage as i mentioned earlier... One size fit all. If they can produce a B+w standard of filter, all the merrier.