Both coolers are about the same difficulty of installation and requires the removal of the motherboard. But are about equally good in cooling performance as well. I would choose the Ultra 120 and have a push-push fans for better airflow and cooling. If you want a good cooler that can be installed easily then I would have to say the Big Typhoon VX from Thermaltake is one of them.
The fan for the Ultra 120 is I think 3-pin which connects to the motherboard. If you get a second fan (preferably and quite one), get the one with a molex connetor and can be powered by the psu directly.
The ultra is the better cooler. I did alot of research and the ultra is is probably the best non TEC air cooling solution out there. However the difference in temps betweeen the two you mentioned is probably 2-3c under load. The ultra is pretty damn heavy too. If i recall the Infinity is much lighter.
That's like saying Godzilla is heavier than King Kong... shrug
Tuniq Tower is probably the best air cooler, but either way, the top are all at the top, performance should all be relatively similar...
Actually i just looked it up. The Infinity is quite a bit heavier weighing in at 2.1lbs. The Ultra is 1.6(w/o fan).
As for the Tuniq, I'm not sure. I havent seen any reviews comparing the two. I have seen many with the Ultra 120 outperforming the Ninja, Infinity, anything Thermaltake, and Zalman.
I just purchased a Vigor TEC to replace my Ultra 120. Ill be doing a review on the temp/performance differences. If any1 with a Tuniq Tower 120 would like to use my Ultra 120 to compare the two let me know. Ill let u use it for testing if you post the results =) (as long as i get it back).
Theyre both very capable coolers than wont vary for more than 2c at heavy load. But the price tag on the Ultra-120 makes you want to go for the Inifity...
You can do push&pull fan configurations with both coolers to extract their whole potential.