Just to reiterate on perception of speed, Joey and BigBad are hitting on it accurately - humans are a really bad at perceiving motion, as we need a frame of reference, such as an object passing by. Without going too deep into the weeds on Theory of Relativity or a neurologic study of how the brain processes visual cues: a study (which of course I can't find a link to at present) was conducted a few years back, where drivers were placed in a simulator, and asked to estimate the speed at which they were "travelling." The visual before them was a simple country road, with trees and other objects placed alongside the road. The study found that humans are really good at determining how fast they are traveling up to 60 mph. After that, guesses were less accurate, with many underestimating their travel speed.
Researchers also added in other factors, such as fog and night time driving, and found that drivers were not able to accurately guess travel speed beyond 30 mph.
All of which is to say, the closer you are to objects, the better sense of speed you have. The less view you have of objects, the less you are able to tell how fast you're traveling (beyond other cues, such as wind, g-force, noise, etc.). And the faster you go, especially beyond 60 MPH, the less likely you will be able to perceive differences in speed.
This can make sense when applied to roller coasters - low-to-the-ground elements and inversions for instance can feel faster, as riders have a closer interaction with objects/surroundings that allows their brain to interpret relative speed. And I also think many would agree they can better tell the difference in speed between 20 MPH and 40 MPH than 70 MPH and 90 MPH. So in turn, while you may be travelling 90+ MPH on one roller coaster, you may also have a better perception of speed on a slower roller coaster which travels closer to the ground and its surroundings (Ala Beast's tunneled double helix). Again, this is in terms of speed as perceived visually - when you add in other factors, such as acceleration on KK or TTD, your body perceives this beyond visual cues as increased positive g-force, wind, noise, etc.
Bringing this back around to Mako, packing in airtime hills and other elements will provide for a good ride experience, even though the ride will be traveling slower than a giga.