My real issue with a map node system is that I loved all the random locations you'd encounter simply roaming about the wasteland in FO3. FO1&2 don't have those, because it doesn't work with a map node system. You can have more elaborate settlements, but what I really enjoyed in FO3 was the physical journey from place to place, something that simply isn't present in a map node system.
Regarding that image, do we have some kind of baseline comparison between square size? The actual number of "squares" is meaningless if a square for one game is bigger than the other. Genuinely curious here.
For example (purely hypothetical) if each Fallout 3 square is, say, 100 sq ft and each FO2 square is, say, 75 sq ft, the relative sizes change drastically.
Squares themselves don't really prove anything without a baseline of comparison between the two.
I also don't really get the abstraction block with a sandbox map; if you can accept that 15 sec of real-time travel on a map node map equates to your character traveling a great distance, why is it difficult to abstract the travel distances on a sandbox map?