I agree with all the other posters in regards to:
- SM is in the dark. Total dark. They name it "space" mountain for a reason. You can literally feel like you are flying through space with all the twinly lights and cars zooming past you.
- SM is "worse" than BTMR but "worse" has a different meaning for everyone.
I happen to love both of them and I don't find ANY Disney rollercoaster near equal to those of universal (with a small exception to Rockin' Roller Coaster)
Now with that being said, you also mentioned Expedition Everest and Tower of Terror....
Expedition Everest is (mostly) and outside coaster. There is a part of it that has a very steep climb and a part where you think you will fly off the end. There is one BIG drop (much bigger than anything on BTMR) but it's over so fast and it's pretty smooth and it curves towards the end so it's not as bad as if it where straight down...
There is also a part that it goes backwards in the dark. Some people feel as though they are going to go backwards and UPSIDE down but you dont. I love the backwards part... but I also love Space mountain and btmr....
Tower of Terror is a whole other ball park of ride.
It's not a coaster at all.
It's a plunge to your death ride.
I will ride it. But I don't necessairly love to ride it. It has a different sequence set up every time so some rides are much more "tame" then others in regards to your "falling" experience. I've been on rides where I almost threw up because the drops were so big each time but i've also come off of it feeling like "that's it?!?" Will I continue to go on it? Of course, will I kick, scream and cry if I miss it? heck no
With my honest OPINION, I don't think you will like space mountain, expedition everest or tower of terror if you think btm is a little scary. However, i'm a firm believer that you should try everything once. If you don't like it, you have a couple options :
1. buy the photo because chances are, it's going to be an awesome memory
2. you'll have something to tell your friends and family about when you go back home
3. it only lasts a couple minutes, disney rides are incredibly safe and you'll never have to do it again
above all else, just enjoy your vacation! Don't stress about missing something if you think it's going to put you in any sort of discomfort emotionally or physically. Everyone knows a
disney vacations is crazy expensive and we don't work or behinds off to save up for these to be stressing out over the small stuff!!!
good luck!!