From the little I've seen of people who've trained both in Spain and the UK (UK IR for me, Spanish IR for a friend and also for my MCC partner last year) a lot depends on the individual. I suspect a certain amount of the poor reputation of Spanish IRs is down to a significant amount of "slower" students going for that option because of the existing reputation for cheaper & easier training - it's a vicious circle. Yes, of course there are benefits to doing the entire course in the aircraft in real flying, although sim training also has benefits when it comes to getting the basics spot on before adding the complexity of the real thing.
Oddly enough this came up in conversations with 2 separate CAA Staff Examiners last year. One didn't discuss the standards, but did say that he could see a lot of training migrating down to the Med over the next few years to take advantage of the weather. The other mentioned a lack of any formal provable evidence of poor training (accepting in all fairness that certain schools do train to a very high standard!) but said that the CAA were concerned about variable training standards when issuing the same rating to everyone.
Maybe it's partly about training for the environment you intend to fly in? Personally, I felt I gained a lot from training to operate single pilot IFR through some of the weather we had last September, without the option to climb above weather. Equally, flying in good weather gives more of a chance to get the approaches nailed perfectly every time. It's always a compromise! On the other hand, I'm somewhat sceptical of places that can complete an FIC in 3 weeks as a friend teaching elsewhere did. Hard to fit both the flying and groundschool requirements in in that time!
Quite a long post I'm afraid, but I'd hope there were a few valid points worth considering there, as well as some middle ways to look at.