Well they are totally different in size, coat etc. They both have the reserved character, I think, with people that they don't know, but I know that with Spanish Water Dogs if you socialise them from an early age that your life and the dogs would be a lot easier.
I always insist with a Spanish that you at the very least do a bit of work with them. When I say work, I mean maybe some obedience, water work (this can just mean you taking them out to your local water park), they are retrieve mad and usually meet you with something in their mouths, maybe something that you rather they didn't!!. All my puppy people register with their local clubs and do some training with them. They are not a breed that could be a single dog and be on their own all day, with other dogs that's fine but on their own I wouldn't recommend it, especially if you are not willing to dedicate your time when you get home from work to them.
The Spanish are very energetic, althought they don't need to be walked for miles and miles and I know that all of mine (5 now!!!) when they are in the house are extremely calm and you really don't know that you've got them. I work full time but before I go to work and when I get home it is their time up until bed time and there's nothing that they like more than being on your knee, they are one of the most affectionate breeds around.
I don't know where you live but if you are ever in South Manchester area there are quite a large number here and you are always welcome to come and see them in their home environment and out at our local water park. There's nothing better than seeing 11 of them going in the water and running around playing. We also have a number of training days at the water park in the next 5 months.
But their biggest difference fromthe Portugese is their coat. You CANNOT, I repeat CANNOT brush or comb the Spanish. Plenty of swimming keeps the coats in best condition and they should be clipped all off, no fancy clip at least once a year.
Oh, by the way, love the previous post:D