Jeff zone 8 N.C.

How much drainage did you have in those whiskey barrels? A lot of people (including myself in past years) drill 3 or 4 holes and consider that enough. Drainage holes are not only for drainage of water but for drainage and inflow of air too. If the wooden rim of a whiskey barrel rests on dirt or a flat floor it traps stagnant air underneath and in the soil. Same can happen with a flat bottom pot, with bottom only drainage if it sits on a flat surface. A potted plant, with good drainage but sitting in a little larger decorative pot with no drainage can trap stale air inside. Plant roots breath just like the leaves and that means they need fresh air too. Watering thoroughly (not just a spritz) pushes the stale air out and so sucks fresh air in. I do not mean to say do that in winter when there is little to no growth going on. No growth = little need for resources. In the last few years I have been not only drilling more holes in the bottom of homemade containers but have been putting holes on the side of the pots too. I have seen a big improvement in growth. Of course PR-Giants coarse sand medium takes care of most of the mentioned problems.
If you mean a "cylinder shape" by saying "straight sided pots" the problem I have with them is the friction when you try to pull a plant out of them. Much harder than a tapered sided pot, like the standard nursery pots.