I am not the one making these informal "rankings." I am just telling it how it is. This isnt an MD vs DO thing, or what is better in practice, blah blah... but if someone on the street were to ask me about US medical school rankings, thats how it goes. I only applied to DO schools and I am into their whole deal, but again, just telling you how it is.
The reason that others perceive even low tier MD as "better" is because of several factors (in this order relatively):
1) The fact that it is an MD school... you cant rank things that half the US population doesnt even know exists (DO). Is it fair? No... is it the way it is? yup, just have to deal with it.
2) More solidified clinical rotations. Not true at all MD, and the opposite is not true at all DO. But to become an accredited US MD school you essentially have to have a core hospital or a hospital region where your students do their clinicals at. This is better than shipping a student 9 hours for a family medicine 4 week clerkship found at some of the newer DO schools... Again... public perception here, you compare a massive hospital complex that takes up 1/8th of a city where students study at vs. private offices in the backwoods. Again, not saying that one is better than the other, as I am in no way qualified to do that. I am just saying how things are generally perceived.
3) You mentioned it... more research. They have more money.. more money means more research... more research means more big name researchers... More big name researchers means more prestige.
Again, I am not selling DO down the river here... but I mean there is no real use in lying to ourselves. DO schools have a certain build, MD schools have a certain build, its just the way things are. This DOES NOT mean MD is better than DO, or DO is better than MD. This DOES mean that public perception and currently program directors at big name MD residencies are biased towards thinking that MD is better.
No need to be ashamed of it or anything, its just the way things are. Accept it... get into a good DO school that you are happy at, do well, and become a doctor. Thats all that really matters, at least to me.