I remember seeing a table comparing corruption figures throughout the world and Spain was only about average on it, something like 14th with the UK listed as 15th. I think Mexico was near to the top.
In Spain I have experienced both PP and PSOE, albeit only at a local level. I couldn’t put a cigarette paper between them.
Mind you, the Spanish news channels are really upset by the Rajoy allegations, and the sheer volume of brown envelopes flying around seems pretty horrific.