Do quality of a butter affect bread texture smell etc etc

It's as simple as that.

However I've no idea what country you're in - where I live, butter legally must contain at least 80% fat. After that its all down to provenance - outdoor/free range reared cows, organic, direct from the farm, supermarket and so on.

I buy butter by the 5Kg stick and it comes from a local(ish) farm via a small wholesaler. It's not organic but the cows are outdoor reared. It's about the same cost as the supermarket stuff, but it also has a slightly higher fat content and I feel I'm supporting small/local businesses rather than the big supermarkets.

-Gordon

Butter has good natural flavour I don't think the same can be said about margarine.  If you are making an upmarket product and butter is called for don't replace it with a lower cost fat.  If you are mass producing a price sensitive commodity then you may have no other option if you want to make a profit.

Gerhard

involves whether / how much the difference is noticeable and whether you think paying the additional cost is "worth it". The former is basically a matter of palates - yours and the other eaters'. The latter is pretty subjective and situational; e.g. you might decide to use higher-cost ingredients when you bake for others vs just for yourself. 

Why not make your own butter? There are numerous instructions online, and you get a better taste in all your cooking.