Car size doesn't really matter. I would be the main driver and do a lot of 2 hour trips alone. The E class is probably big enough, although my old 126 had a big and comfortable back seat. I'm sure when I have passengers that the 140 would be better, but that's not that often. I've ridden in the back of our 210 wagon and it's OK.

The 210 has rear side air bags and head air bags. The 140 probably has stronger doors / passenger cage (that's a guess on my part). Which is safer - tough choice.

Maintenance wise, both are the last of their model years. The 210 may be easier to work on but I'm sure there is not a lot of room under the hood.

Fuel economy should be close.

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07 E350 4Matic wagon, 06 S430 4Matic, 99 SLK 230
retired W210 (x3), W124, W126