Travis,
There is no way to tell for sure without some very intensive quanitative analysis and logirithimic formula computations.
It would be easier to determine the correct answer if the inventory was always the same. For instance, Say every 10x30 unit had 10 washers, 25 vacuum cleaners & 200 DVDs & every 10x10 unit had 2 washers, 20 vacuum cleaners & 100 DVDs then it would be pretty easy to track the data on how much you sell each of the three items for and how long each item takes to sell.
The problem is each large packed unit is different and each small lightly packed unit is different. Different inventory, different quality, etc.
You could end up buying one large 10x30, take a month to sell it and make $2500.
Next month buy 4 10x10, take a month to sell them and make $4000, and then concluded buying the smaller units is better!
But, you could just as likely buy one large 10x30, take a month to sell it and make $4000.
And the next month buy 4 10x10, take a month to sell them and make $2500.
It seems like the issue is limited space so the supposition is if I have 10x20 space for buying storage units it's better for me to buy 10x10 or smaller units, move them out quicker and not have all my space taken up by one 10x20 unit.
A couple of thoughts. Isn't inventory just inventory no matter how much space it takes up? So is it more cost effective to continue driving back and forth to auctions and storage facilities to buy and clean out smaller storage units instead of having that one large unit taking up my space?
Generally, the quality of a unit tends to be the same through out. Do I risk not buying a good quality 10x20 or 10x30, just so I can take some wacks at some good, fair, or poor quality 5x10 & 10x10 just because I can move them quicker?