Relative of mine is looking into an E350.. which I'm not a huge fan of, but does anyone have a summary of any differences between model years? I can rattle that off off the top of my head for my 211, but that was after a year of looking at them and figuring out the differences myself.

The relative or the car?

2010, 2011, 2012, 2013 mainly had just minor exterior differences such as the outer daytime LEDs.

Also, 2012 and 2013 have colored dashboard display instead of black and white that 2010-2011 has. I think late 2011 models have color displays as well

2013 also has a different colour theme than the 2012. 2013 has gray/black theme while 2012 has a warm yellowish colour theme.

Also, for the 2012, the engine has more hp and people say that engine is more reliable/better than the previous one.

Also, the tail pipes are different between the years. I think the 2010 had round tailpipes instead of the square ones for 2011+.

Other than that I cannot think of anything else.

Blue Efficieny badges were deleted in later models as well
Besides for AMG models (not including E63 ) design of the steering wheel was changed to a sleeker one

I have a 2010 model with square tail pipes. I think it is in all Sports models.

The Comand changed in 2012 from 4.0 to 4.5, right?

Yes that's correct. Hmm maybe the square pipes are on sports model then. Not sure about that one.

Yes, the square or rectangular tail pipe tips are on the sports models and the oval shape on the luxury.

Except the 2011 (at least) E550, where the Luxury has rectangular tailpipes. (Photo below)

I'm sure that the circle ones were only on the earlier models. The 2010 Luxury ones to be exact?

what does the poster mean by a different color theme? warm yellowish or grey and black?

By that I mean on the Center Console display and in-dash display, the background colour on the screen is yellowish for 2012s. For 2013s, the background color for the 2013s are black/grey.

Also for the 2013 the In-dash display have the option of seeing a ECO bar.