I purchased a 2TB ac Time Capsule instead of the 3TB -- by the time I need 3TB, larger drives will be available for less than the $100 difference.
As to other router and back-up options, there are certainly great choices -- the ac version of the Asus 66 series has range slightly better than the ac Time Capsule, and more user-customizing features.
I went with the Time Capsule because the ac performance is still excellent, I don't need the extra settings options, and staying in the Apple eco-system made my life easier -- I have precious little "me time", and the total hardware/software compatibility means that I'm much more unlikey to have to spend that time on configuration and compatibility issues.
FWIW, I'm not an Apple fanboy, but where 25 years ago I enjoyed spending great quantities of time putting together PCs from parts, I'm now at a point in my life where I am Apple's ideal customer: someone who wants top-level hardware/software that, pardon the Jobs-ism, "just works" out of the box, because I no longer have the luxury of giving major tinkering time commitment to new gear.