Actually I think TOGA might have a pretty good idea about the differences... When's the last time you were in a Legacy? It was about 30 minutes ago for me...
The Legacy and Legacy Exec are very similar to each other. However, they are a lot different than the straight 135 (the same as CoEx, Conoco, and EJM -- Intel) are flying. The fuel system is totally different, there are winglets, different interiors, and different numbers of doors/exits (there is a full galley in the Legacy and no service door, for example). So, as you suggest, I am reading the above posts and pointing out that they are not correct...
Bad-Andy (145, 135 and Legacy CA)
Just for reference, Options has a few of the original Legacies (A1/P, wipers, 13 pax config), Swift has a couple of the new Legacies (no wipers, A1/E) both here in the US and in Kuwait, and a company in Scottsdale has at least one Legacy. All the other ones flying around are straight E135s.