The "key differences" would be their motivations - fear of being corrupt/defective vs fear of being worthless and having no value. So to really understand the difference between 2w1 and 2w3 you'd want to understand the difference between 1 and 3 themselves.
Behavior between the two is a lot more fluid because types themselves can be so diverse. But on a general scale, I guess some big differences would be that 2w1 is more principled and perfectionistic while 2w3 is more histrionic and expressive.
I think a lot of people pigeonhole 3s as using status-markers as their
only means to feel worth. I honestly believe 3s are a lot less ambitious and ladder-climbing than they're made out to be; having a "big personality" in and of itself can be impressive. Not to say all people in theater and the arts are all 3s, but living in NYC I think there's a culture to them that is very 3. To get the part and make it big you have to stand out apart from the others. I've met some interesting personalities and while they didn't actually seem very status-conscious or anything like that they always stood out. I think that has a lot to do with 3 - if you stand out in people's minds, you have worth. I'm willing to bet a lot of "comedic" personalities are actually on the 2/3 spectrum rather than 7 (
down with another stereotype [MENTION=10082]Starry[/MENTION]?) because the funny/goofy person does make you feel like you are loved and that you have worth. So I think 2w3s get the "extroverted" rep because there's more of a focus on standing out, being a memorable person, etc.
2w1s I think are a lot less direct when it comes to trying to draw out feelings of love and appreciation. I could see this type dealing with a lot of internal conflict, 2 wanting to get others to make them feel loved while 1 is in the background saying they need to be more rational/principled. In the past my INFJ 2w1 friend suffered in silence a lot as she felt she didn't get the appreciation she deserved despite being such a good friend. I think 2w1s might be more likely to emphasize being a "good" person to receive love because of 1's need for righteousness. Also since 1 is a gut type, 2w1s may struggle with rage more than 2w3 whose needs are completely tied to shame. Also in the case of my 2w1 friend, she definitely exemplifies the "8s in chains" aspect of 1. She has a lot of rage and would rather just steamroll everything in order to get what she wants, but because of her need for integrity she controls herself and channels her rage in a more purposeful way. This also augmented her frustration as she WAS being a "good person" in order to be more lovable, but she wasn't getting what she needed and but she felt like she still couldn't let loose as she was bound by those chains. Happy ending to the story - she learned to accept her anger and negativity and feels more like herself than ever before.
Hope that helped~