I'm not a musician but I'm considering buying Logic X. I edit short corporate videos on FCPX and I use the Apple soundtracks and loops supplied.
Now i know Logic X has tonnes of instruments but does it have complete short duration soundtracks? or loops?
The typical ones I use in FCPX are between 30" and 2'30" and are found in "Apple loops for soundtrack pro" folder in FCPX.
It has what you get in FCPX, pretty much. Logic may give you a few more loops. But, you can put them together and create whole compositions much easier, export them as AIFF files for use in FCPX. Be aware that XML between FCPX and Logic X is totally broken. This was slapped together in Logic X using nothing but loops.