Thank you all for your awesome responses...Icon: Great pics!!
I think I'm set on a pancake and here's why: I don't have one yet. I have plenty of awesome bokeh-licious fast lenses (O45, O75), but nothing that's truly tiny.
However...I think I'm going to go with the P20, and here's why:
1: I'm buying it out of "free money." I just moved into a new apartment and sold an oven the previous tenant was too lazy to move and I bought/sold a camera for a profit over the past weekend...between the two of them, I made just enough to pay for either lens. May as well make the most of it.
2: I've been doing a ton of comparisons, including mocking up things around my house to match the size of the lenses, as well as scaling pictures (thanks to camerasize.com on this one) on my screen to be exactly life size...and, really, that 5mm thickness difference between the pancakes really isn't that big (and I'm not concerned about the diameter difference or the negligible weight difference).
3: 1.7 vs. 2.5.'nuff said! I've been dreaming of having an arsenal of fast lenses...2.5 is nice...1.7 is incredible!
4: I have owned a 40mm pancake on full frame before and absolutely loved it as a walkaround.
5: I have two lenses already that cover 14mm, but only one that covers 20mm, and it's a big lens (12-50), whereas a small lens (9-18) already has the 14 covered. Furthermore, the fastest 14mm I have is f3.8 right now, about a stop slower than 2.5. But the fastest 20mm I have is f4.6...two stops slower than f1.7.
6: Neither is a bokeh monster, but in a pinch, the 20 does it better than the 14. In fact, while both lenses sound excellent, as far as image quality goes, the 20 seems to do everything just a little better.
What do you guys think? Am I crazy, or does this all make sense?