I'm going to build new PC and one of keywords is durability.
Options so far:
Asus Sabertooth Z77
In warranty point of view only in Asus Sabertooth Z77 has 5 year (other has 3 years). Is this enough detail to choose Asus or is there real differences between Asus TUF, Gigabyte Ultra Durable or MSI Military Class III technologies?
You have chosen the three best motherboard brands for quality/reliability. GIGABYTE, ASUS and MSI all make very solid boards and there is really not much between them in terms of quality/reliability. You can't go wrong with any of them.
At the moment GIGABYTE and ASUS are slightly better than MSI in regards to quality. This varies between motherboard generations though. For example, GIGABYTE was the best for reliability for the outgoing P67/H67/Z68 generation, whereas ASUS was better for the P55/H55 range. Who knows which will be better for the z77 range?
If you are buying this board for the Ivy Bridge I recommend that you wait until the Ivy Bridge CPUs are actually released -- giving some time for these boards to be reviewed, and the choose on the recommendation then!
Also In general make sure that the motherboard has Japanese made solid capacitors. GIGABYTE brands these "Ultra Durable", MSI: "Military Class" and ASUS: "100% solid caps" or something or other.
Another consideration is: GIGABYTE make all of their motherboards in Taiwan, whereas ASUS/MSI have factories in China. The manufacturing process is pretty similar otherwise, just some people believe that Taiwanese made products are slightly better quality.