Heh! I've got a Tuniq on back-order... so I can tell you, from personal experience, that's one MAJOR difference. You can pick up a Scythe Mine anywhere. Tuniq T-120s are scarce as hen's teeth!
Secondly, the Tuniq is made for massive cooling. It'll dissipate, like, 200w with no problem, if you blow enough air through it, but its' design requires a LOT of air! So, if you want to make it work to maximum efficiency, it going to be noisy... guaranteed!
The Scythe Mine, on the other hand, is designed to the quiet. It won't dissipate anywhere near the same amount of heat, but it doesn't require a lot of air either. Basically, the Mine is designed to work somewhat better than a factory reference HS, with a LOT less noise.
To exemplify the noise situation:
Almost every review I've read on the Tuniq has commented about how loud the fan is. You can always lower the fan speed, of course, but the cooling drops off rather quickly because of the tightly spaced fins, and so forth. It's not a good candidate for low fan speed operation!
However, every review I've read on the Mine has commented on how quiet it is. One reviewer said he had to get a flashlight and look inside the fins, because he thought the fan was dead! It wasn't! It was just that silent...
To wrap this up, IMHO, while they look similar in design, they're really two different animals. So, it all depends on what you're looking for -- maximum cooling and maximum noise, or minimal cooling and minimal noise.