Huh?
You know you can put the mini just about anywhere you want? I put mine behind my Thunderbolt display. As clean looking as a imac.
The Mini is easier to sell. How is it easier to sell a monitor with a computer attached? Shipping is alot more and shipping is a hassle selling a imac. The mini is in a neat little box. Can be put in it's original plastic wrap, if you are care full you can remove the mini without messing up the plastic wrap that surrounds it.
The display on the imac is great, but expect some more yellowing than a monitor without a computer attached. The heat from the computer causes the yellowing. If you hook it to a external display you don't have that problem. My thunderbolt display looks better than any of my 27 imacs. Cooler colors no yellowing at all.
The Mini actually holds it's value more than the imac, actually much more. I don't why you had so much problem selling yours. I sold mine last year for more than what I paid for it after adding a SSD and Ram. Something that is actually difficult on a imac. I actually made a profit selling it. I was not even looking to do so.
With the mini, you can practically change the computer every year or two and hardly lose nothing or gain a slight profit. You can keep your monitor for a longer time period making upgrading more often cheaper than a imac would be.
Seeing that the new mini's have more horsepower under the hood than the stock macs and the top mini can match the top imac. Other than the GPU the mini's wins in my book, hands down. That is just my opinion, your mileage will vary.