Sony TV's - Bravia engine 2 v Bravia engine 3 difference?

The old which flat screen TV question again.
What would be the visual obvious difference (besides price) on a Sony:

KDLex500 and a
KDLex503?

Both have the 100hz refresh rate from what I can gather. I'm talking about a 37 or 40in for general living view TV watching & Wii playing...

Here's a bit of info asking same thing from the renowned AVForums site.

http://www.avforums.com/forums/tv-should-i-buy/1096868-bravia-engine-3-vs-bravia-engine-2-a.html


Plus some of Sony's own blurb
[broken link removed]

And another
http://www.ehow.com/facts_7594054_sony-2-compared-engine-3.html