Solitaires look lovely; you will not face an argument there. However, cluster diamonds are not bad either, although not as appealing from a classical perspective. If you are tired of the single stone design though, a change may be what is called for, and cluster rings can provide just that.
Cluster diamonds cost significantly less, which is nice. This is mainly because they comprise scrap diamonds left over from the shaping of larger diamonds, while solitaires are those bigger diamonds. With that lowering the cost, people with a budget to watch can take the option of a beautiful set of small stones, which looks wonderful on the right finger.
All jewelry loses its showroom value after being used long enough. The factor contributing to this, for the most part, is wear and tear. Diamonds are hard, sure, but they can be lost quite easily if not set in the right way, or dim from accumulated dust and dirt. When considering these things primarily solitaires come out on top.