I've owned both,
The UDT is great, perfect fit/finish.
The fit/finish of the 705 I have is slightly behind the UDT, but there wasnt anything about it that was bad.
Durability wise, neither of them would break on you.
The UDT does have a spring though, and those do break, though not often.
Same with the Axis omega springs.
The tip on the UDT is thicker though, so it would also be stronger.
Locks...Both have absolutely secure locks.
A botton lock is one of the safest, if not the safest.
Same for the Axis.
There is an advantage in closing the knife. With the 705 you dont have to close it against the tension of a spring.
The UDT may be a tiny bit better for wet conditions, especially if you get one with a coated blade.
The T6 handles can't rust like the liners in the 705.
The handle also curves slightly at the bottom, giving you suposedly a better grip.
That brings me to the handles.
A drawback of the UDT is usable handle size. I have medium hands and I can't get all four fingers on a UDT handle. On my 705 the handle fits better.
I think it's because the UDT handle wastes about half an inch by adding that guard looking thing.
I'd try to handle one first, they're very different knives.