I wouldn't ditch one for the other, but I agree that "Coastertube" more properly defines what it actually is (which is a dedicated niche topic with videos in the style of YouTube.) The mass amount of people, especially "non-geeks" that may wanna try to find a POV of the coaster they just went on, would probably be immediately drawn to something that literally defines itself as "youtube but with coasters instead."
I can think off hand of several other "tube" sites that feature niche topics. Good for you for snagging the one related to coasters, and I think for that reason alone you should "market" it under Coastertube. Easy to say, easy to remember, and it defines itself in the title.
Given the pretty wide range of the videos you guys produce, having a collection of videos dedicated to the more personal, fun and wacky antics could be labeled as "TPR TV" which feels a little more community based.
Someone already mentioned a Podcast as well, and I think that is a GREAT idea. Like any certified coaster nerd, I usually (to my social demise) really enjoy talking about roller coasters and hearing others talk about coasters, especially ones I haven't been on. Having a "radio style" Podcast where you guys review coasters and parks, discuss future trips, have people call in for trip planning advice, and even interview industry folk (like the guys from GCI) would be AWESOME. I would download the hell outta those. Just like Leo Laporte does with tech gadgets, you guys could do it with the amusement park industry and (I think) have quite the following.
-Mike