slo-mo vs. timeline frame rate change

I'm being given some 720p HD footage shot at 30fps and was asked to edit in a 24fps timeline to give it a slightly slower ethereal feeling. But I'm wondering if the visual result of this approach would be any different from what you'd get by using a 30fps timeline and manually slowing down the footage by the appropriate percentage? In other words, would the video look/feel the same in either approach, or no?

Obviously I'll try it myself, but I don't have the footage yet and was wondering if anyone had done this comparison before.

And whether it would matter if one were using FCP 4.5 vs. 5 (on a dual 2.0 PPC G5).

what's your delivery format?
if it isn't 24fps dont work in 24fps.

you;re right, the best approach is to slow the footage down slightly.

unless the delivery format IS 24fps