I've heard from a couple different sources the idea that the "ukemi model" for teaching is a bad one because it teaches us to give away our center. My understanding is that "proper" ukemi demands uke try to be nage (i.e. tries not to just give it away, but to hold onto it, especially when in compromised situations); nage and uke are trying for the same thing (displacing the other person). I can see how simply going for the fall ("tanking") is counterproductive and potentially dangerous; I can see how just allowing nage to move you no matter what is also counterproductive...But isn't the "ukemi model" only half of the "nage/uke model?"
Despite being fairly new to Aikido, I quickly see a huge benefit to taking ukemi, but maybe once I get less new this will change.
So I have two basic ideas I'm hoping to get addressed here: I'm curious if a distinction could be made on what exactly is meant by the Ukemi Model? Also what are the pluses and minuses that you find come from your study/practice of ukemi?
Well the use of such an all encompassing phrase to describe one specific type of practice is a mistake. It's not the connection most people making when hearing the phrase and usually just irritates people. Nearly every time you see it used you end up seeing post after post where the person who used it has to go back and explain that it's intended to apply to that one type of practice. It should be flushed down the toilet.
There's nothing wrong with ukemi itself, it's the intent behind the practice that matters. As you said, are you trying to displace nage? Are you trying to upset their balance, control them in some way, stress them in some way? Ukemi should be what happens when you're doing that and they find a way to counter what you're doing, take your balance and/or control you. Doesn't matter if the practice is internal or external, same same.