If the voltage rating of new capacitors exceeds that of the capacitors being replaced, and if the physical fit is right, there is no disadvantage other than cost in using same capacitance/higher voltage units. The 47µF caps are mostly doing filter/reservoir work, so accuracy of ±10% in value is acceptable. Putting in 33µF caps will not kill anything, but it diminishes the capacitor's capacity (pun intended) to do its job by a greater margin than 10%, that's all.

If you are considering standard aluminium electrolytics at the moment, why not drop jdw a PM to see what he thinks of his own use of tantalum electrolytics on one of his boards.

de