There's a lot of model numbers to go along with a very large number of different models from different manufacturers, you can make comparisons based on the parts inside.
Refurbished computers are common because the average turnover for a desktop PC is about 3-5 years, however the average shelf life of a desktop PC is about 10-15 years. Which means the system still works after the original owner discards it. Another source of refurbished computers is schools and businesses which buy hundreds of the same system, and 5 years later replace them (usually needlessly) and the old systems are scalped for a minimal profit.
Buying from an online auction is risky, generally speaking, as many people out there are just trying to rip you off and take advantage of you. However, buying refurbished computer hardware (when its correctly refurbished, as in factory refurbished) usually saves you a great deal. There isn't much you can do to "damage" a computer, its either broken or working, so if its been discarded because the original owner doesn't want it for whatever reason, it should be entirely capable of continuing work for another number of years.
I'm sure there are a number of members here willing to help you make an accurate comparison of two systems, if thats what you're after.
Re the sub-par question, normally if a particular model line is known as terrible, it doesn't resell very well because IT managers know to be wary of it.
I'm curious as to where all of the refurbished computers offered for sale come from, why there are so many, and are they worth considering buying?
I would think having a lot of a certain model being offered as "Refurbished" would be indicative of a sub-par product.
Am I just asking for trouble considering a computer offered at an online auction? There is a lot of stuff out there.Why are there so many model numbers? It is very hard to make comparisons.