Default Refund or ANOTHER Replacement?

I've now had about 6 or 7 replacements of Nexus 5's with varying ***K numbers and finally Google have asked me if I would accept a full refund instead of a replacement.

The main issue I've been getting that isn't being fixed by them is nobody can hear ever me properly as it's always muffled on their end although I can hear them perfectly.

If I were to get a replacement, there's a 99.99% chance that the issue will still be there but I love everything else about the phone too much.

If I were to get a refund, what alternative is there that's as good as the Nexus 5 offering a pure Android experience?
iPhone 4-->Nexus 4-->Nexus 5-->Moto X
Nissan 200SX/Silvia Tuning Guide