Niether is more important, they are equality important to each other.The modelling needs to be clean and functional for what it has to do and the texturing can make or break a model.

There is certainly no harm in spending time modelling because the more practice you have the better and more importantly faster you will get, however some things are simply not worth the time it would take to model perticularly if the item will only be seen for an instant or from a distance.
It is a judgement call on your part if it's a personal project as to what needs to be modelled and what can be bumped or displaced.
Another factor is rendertime, increased polycount might increase rendertime more than a displacement or bump map ,so again a map might be a better way to go.
In a production environment other factors might effect the decision like polycount or an art director wanting a perticular look.
The bottom line is it's about getting the look required in the fastest most productive way rather than the most perfect model ever.

Hope this helps a little with your question.