hi,
as asher pointed out, making a full conductors score is perfectly possible with logic, but there are issues, little problems, limitations and work arounds that have to be known about to make it a smooth experience.
also, as asher again pointed out, there are many things that are fast on logic than in other dedicated notators, and in general composing the raw material is easier faster and more flexible than a dedicated notator. at least over on this side of the pond, working in logic and exporting to sibelius for the final result is very standard way of operating. now, there is a PDF to XML application which some of us here (not me though - not tried it) have had great success with. i think william levine who does a lot of orchestrating in logic and recommends it.
if err...you can pardon the forwardness...i have on line some sample scores that might demonstrate what is possible in logic.
http://www.rohanstevenson.com/
and go to concert music. 'black ice' or 'devil' are full orchestral scores.
finally, if you do want to get your feet wet with scoring in logic, aside from j prischls tutorial, my mine bit of advice is to understand to concepts thoroughly - everything else will follow from that.
1) score styles. you can have as many as you want on a track/instrument
2) instrument sets. set a KC for their creation. understand what they are and how you can use them to create parts as well as help you edit. incredibly fast and flexible.