I've had the Sony Xperia Z1 since it was launched and it hasn't failed me so far (except for a battery replacement with a re-sealed back at the official repair centre). It has dropped on the floor several times and I haven't had any issues with glass breaking or cracking at all
chiefie: Electronics and salt water don't mix too well... they may be able to carry on functioning but be careful with erosion.
I've noticed that the phones are more susceptible to problems from dishwater which has affected the speakers and microphones more quickly. It is real obvious when this happens which is why I noticed it. I assume that the detergent reduces surface tension so the water can get in to smaller gaps more quickly.
With salt water I've just washed the phones in tap water to get any salt residue off.
If it were between z3+ and z3 I would take the z3 as it has better battery life as shown in reviews I think the sd810 has alot to do with average battery life in z3+. The camera is the same apart from the front having one and the z3+ has an uncovered usb port. I value battery life and the rest doesn't matter for me that's why I'll go z3 over z3+
The Z3+ battery is also 5% less powerful at 2930 mAh versus 3100 in the Z3: http://pricespy.co.nz/category.php?k=103#rparams=m=s239017006
Unless you really need good battery life then I'd prefer the Z3+.
If the Z3 and the Z3+ had the same chipset then I'd go for the cheaper Z3. But that is not the case. The externals are twins [Edit: near enough anyway] but chipset is very different which means the Z3+ has a major performance advantage: Dual quad-core CPU instead of quad-core Better graphics capabilities Better codec support ie full H.265 Dual-channel 64-bit RAM rather than dual-channel 32-bit RAM
The hardware is different so it will be a different Android build which might have a small chance of being better supported for longer.
Forgot that you mentioned the HTC Desire Eye. I'd put it third unless you like HTC or want a colour that Sony don't have. I like the matching cameras but in general the HTC is not better than the Sony models.