Using a secondary for a couple weeks would be preferable to letting it in primary for 3 weeks... Sitting on the trub that long MAY contribute some off-flavors. I have let beers sit in the primary for 10-14 days before when I got sidetracked with other things, and there appeared to be no real harm.
Why take the risk though? Rack to glass secondary, let clear 7-14 days, then bottle...
From my experience, you will absolutely have less sediment in the bottles if you use a secondary. Beers (2) I've bottled without secondary seem to have a noticable amount of sediment in the bottle (several mm or 1/8"), while beers I've secondaried (5) have almost no noticable sediment. A slight yeast 'film' on bottom (similar to what you'd find in a Sierra Nevada Pale Ale) but that's about it.