Even though this attraction has been around awhile, if anyone doesn't want spoilers, don't read my post.
This is my favorite attraction. I have been on it MANY times at WDW and just rode it for the first time this month at DL. I had the same questions you do.
The one at DL does NOT have random drop sequences. I specifically asked the CM's about this. The ride seemed the same to me each time at DL.
The CM at DL said that they eventually put in the random drops at WDW because the attraction had been there longer (10 years???) and they were starting to not have as many riders. So to rekindle interest they added the random drops.
At this point in time he claims the one at DL is new enough that they don't "need" to add the random drops yet to attract riders.
Regarding the elevators, at WDW they do move out of the first shaft and travel through the Twilight Zone "room" and then lock into the second shaft to do the drops. The one at DL does NOT ever move out of the original shaft. (Cost cutting IMHO).
The one at DL does not have a Twilight Zone "room" like the one at WDW that the elevator travels through. A previous poster referred to the Twilight Zone "room" at DL, meaning the first room that you stand in and watch the Rod Serling TV set. But the weird, special effect Twilight Zone room you travel through with the "eye" etc, is not at DL at all.
I did like the one different "scene" that is at DL that is not at WDW. When you first begin the elevator part the doors open and reveal a huge mirror effect. But overall, I just prefer the one at WDW.
I really prefer the whole entrance at WDW. The whole approach of walking uphill to this huge building and the whole decaying and unattended gardens/empty fountains with the steamy/fog effect and then the balcony right before you enter the lobby sets the atmosphere and makes me feel like I am leaving a theme park and entering a real abandoned hotel.
The one at DL feels to me like it was just plopped down at the end of the street and not a lot of thought went into theming as you go up to the front and wait in line outside.
Also, I noticed a big difference in the CM's. The ones at WDW have always been in great, serious, character but the ones at DL were talking to each other, laughing, or seemed bored. The only "getting into character" we saw them do was when they did the little speech before the elevator doors close - and it seemed like that was just an afterthought - like "Oh, yeah, I'm supposed to do this little spiel (sp?) and act intimidating, well, let's get it over with".
I had read up about the differences before we went to DL and I am glad I did because I was prepared for it not being quite as good as WDW and therefore I was able to enjoy DL's version for what it is. If I had no idea of the differences and went to DL expecting the WDW version, I would have been REALLY disappointed. That's just my opinion.
I know my post sounds negative about the DL version. However, I DID enjoy it. I guess I would sum it up like this: If I had ONLY gone on the DL one I would be raving about it. But comparing it to WDW, I would pick WDW's version everytime, hands down.