I had, and still have, the attitude that BZE offers tons more content. If BZE was like the old BZ1.8, I'm sure I would have contributed more to testing 1.5, in the pursuit of the stock game.. BUT BZE has the stock game. That's the critical difference. AND it fixes or subdues many of the notorious bugs, such as the timer bug, the east-west bug, and several others that most players would not even notice unless they played daily, adds tons of BZ2-ish maps and ships, adds Dx9 support, adds filters to the setup screen, adds audio to the lobby. . .I could go on, but it's really a waste of time describing them all since there's noway anyone cares at this point if they haven't already tried it. I've also wondered several times over the years if BZE didn't hurt itself with some. . .well. . .let's say, was unconsciously too hard on their intellect.
If we're talking online play, there's simply no comparison. Those that choose BZ1.5 because they were told it's "more pure" has been fed so much kool-aid over the years, they have no clue which end is up. But that's only the fault of the flock, so I don't entirely fault the kids who play only 1.5. But let me be honest. BZ1.5 does indeed offer one strong attribute over BZE, and that's the ability to play the SP.
Ken's a nice guy, he's constantly supporting BZ with his precious free time. Psychotic Rhino needs to take a chill pill and quit complaining, and stop being so ungrateful. Movable window in BzE? ALT + ENTER fullscreen/window toggle in BzE? Maybe Psychotic Rhino should show some gratitude since Ken programmed all those enhancements and they showed up in BZ 1.5 before they were added to BzE. In fact, ALT + ENTER toggle was my suggestion. 
