Personally I like the packing folders better than the cubes, but use both. I am pooh size and can pack 8 pairs of shorts and 8-9 tshirts/tanks, plus a maxi sundress in one 18" packing folder which fits perfectly on one side of my Hey's spinner carry on. It's really full, but as long as I can get the velcro flaps to meet, it holds. I then slip a pair of flip flops in at each end and clip that half of the carry on closed. In the other half of the carry on I put packing cubes. I usually have a small packing cube that holds bras, panties, and a night gown, then another that holds odds and ends and leave some space left over (since stuff always seems to take more space coming home

). I can pack for a 9 day trip using my 21" Heys spinner and a personal item (usually a small Vera Bradley duffel or back pack). I normally use the slim cubes and small cubes more than the other packing cubes, but have them in just about every size. I usually put blouses and shorts in packing folders, but if ai was going to put them in cubes, I;d proably use the medium size ones. I also have the 15" and 20" packing folders, but use the 18" more. The only time I use the 15" is if everything doesn't fit in the 18" and I have just a couple of outfits that I put in the 15" then add that to my personal item. The 20" folder I only use if my husband and I are doing a checked bag.
It just seems like I can squeeze more into a 18" packing folder than the packing cubes. Use the guide that comes with them and clothes don't seem to wrinkle as much either. As long as you can get the velco flaps to close, the packing folders will hold, so you can really squeeze alot into them. I always arrange my clothes into outfits, then fold them into the packing folders in the opposite order that I'll be wearing them, so the first day's outfit rounds up on top and the 9th day's outfit on bottom. When I get to the room, I just open up the packing folder and place it on the closet shelf and then each day's outfit is handy in the order that I'll be wearing them.
Just FYI: I got my first packing folders and packing cubes from ebags, and then ordered some of the smaller quarter cube size cubes from Zappos, but later actually found them alot cheaper at TJMaxx. The ones at TJMaxx were also the good Eagle Creek ones.
This is the carry on I usually use (except mine is an older plaid color) and the 18" folder fits perfectly in the side of the carryon that clips closed (the top side--on the left):
http://www.luggagepros.com/disney-b...utm_term=Disney by Heys&utm_campaign=PID15967
Read the reviews for packing folders and packing cubes on ebags and zappos:
http://www.ebags.com/product/eagle-creek/pack-it-folder-18/147919?productid=10019024
http://www.ebags.com/product/ebags/slim-packing-cubes-3pc-set/107842?productid=10150082
http://www.ebags.com/product/ebags/small-packing-cubes-3-pc-set/93507?productid=10152615
http://www.ebags.com/product/ebags/packing-cubes-3pc-set/13032?productid=10150076&rlid=DETAIL
http://www.ebags.com/product/ebags/large-packing-cubes-3pc-set/48438?productid=1234148&rlid=DETAIL
http://www.zappos.com/eagle-creek-pack-it-quarter-cube-zambia
http://www.zappos.com/eagle-creek-pack-it-double-cube-zambia