I've always been partial to Les Pauls, and considered them my #1 go-to axe. However, I've wanted an ES335 since I first played one in 1969, but could never bring myself to part with the $3000 + that they want for them. In 1993, I bought my first Epiphone Dot at a yard say for $75 w/ hardshell case. Needless to say, I didn't haggle. In 2001, a friend who owns a music store sat me down blindfolded and gave me an ES and a Dot to play. I couldn't discern the difference and promtly bought my second Dot. I have since owned two more (4 altogether). One I purchased from Musician's Friend and when I ordered it, I called the company about the difference between the Dot and the ES. As luck would have it, there was a Gibson Rep at MF that I talked to and was informed that depending on year and model they ranged from no difference at all to negligible differences, mostly in pickup quality and/or tuners, which are both easy fixes. But the stripped down versions are identical and in some cases (again, depending on year and model) EXACTLY (other than headstock) identical.
I consider this to be the definitive info: http://en.wikipedia.org/wiki/Gibson_ES-335