Personally, if I can hear the difference, then one set must be pretty poor. Frankly, all I hear are different tonal characteristics, not better or worse. I have access to, but don't own, a nice pair of expensive preamps. It takes me a twenty minute drive to collect them. This is enough for me to rarely bother. I find the same kinds of differences with my mics, so I am very happy with the options open to me without going for large ticket preamps with my money.
I can hear bad ones, less bad ones, OK ones and good ones. However, I'm totally open to the normal ones being used for pretty well anything. I have far more grief with producing the stuff the mics capture. I know that posh preamps make an audible difference. I just cannot determine if it is better, or just different. I'm not certain that what I hear is actually 'better'? Once the hiss has gone, then I am happy.Tonal changes I can create with mic choice and eq. I am also totally unsold, and always have been, that tube circuits are better. I accept many people like their results, and I can live with this opinion, but I don't share it. I have some quite elderly mics in my collection, and if you arrange them into date order, this is also the same order you would get if you sorted them on top end clarity and presence. I had some old but perfectly functional STC mics, and I hated them. The money from their ebay sale generated funds for new brighter ones, which have worked well for me. Warming up the sound with flash preamps isn't on my list.