Hi Jamie12, I can only comment on Zwartbles as pets. We bought 4 ewes about 13 years ago and have loved them to bits. Our original choice had been something else, but then we came across Zwartbles and nothing else seemed right after that. We had the last two put to sleep last winter (but had already prepared for that by buying 4 more). They all reached the ages of 12 and 13.
So - they are big and cuddly. They are exceedingly friendly and gentle, although as they are big and strong they can unintentionally knock children (and the odd unaware adult!) over. We struggle to turn ours over, so my advice for foot care would be to train them to hold their feet up like horses. You don't get such easy access, especially to the back feet, but it's the best we can do. Another tip for turning - get them up against a wall (we're lucky as we have stables for them), pin them there, reach through their legs so one hand grabs the front leg nearest the wall and the other grabs the back hand nearest the wall. Then pull those two legs towards you away from the wall, the idea is that the sheep slides down the wall and ends up lying on her side. It's not best practice, but it's worked for us on the odd occasion. Having said that, our shearer flicks them over with no effort at all - our technique is clearly lacking!
We have never lambed ours (knew I'd never be able to get rid of any of the lambs and we can't end up with 50 sheep!), but in the first few years we made the mistake of still feeding them grain. I now know they don't need it and they did end up a little fat, which in the long run isn't good for their hips and legs (arthritis got 3 out of the 4 in the end and the extra weight didn't help). Now they just have grass and hay which we feed ad lib when the grass is poor. And the odd bucket full of grain, just because I can't help it! They have been exceptionally easy to bucket train and will come running at the sound of it, and also a rustling plastic bag because that signals treats - fruit, veg, the odd digestive biscuit.
They are very easy to catch for checking things out. In fact, I can walk up to them in the field and they will stay lying down while I put a head collar on them.
They are a milky sheep and we have had some trouble with full udders in the summer even when they have never had lambs. One ended up with an abscess filling her entire udder, but she was about 10 by then and it never caused any problems. We've had no problems ever with flystrike (treat with Vetrazin) and they've never been ill (treat with Heptavac). They have had limps and the occasional 'something' when I've felt that they were under the weather but that's all been easily fixed with antibiotics, pain relief and rest. That's not to say we have't had our share of dramas - rhododendron poisoning (recovered), trip to Royal Vet Hospital when I though abscess was cancer, cyst on head which did turn out to be cancer (treated as cysts for a long time, but after realisation struck we had to put her to sleep).
Sorry, I've just read through your original question and I haven't really answered anything you wanted to know! Nor did I intend to give you their life story. Guess what I wanted to get across is that if you are tempted by Zwartbles I don't think you'll be disappointed in their personality, their gentleness, their friendliness, their looks or the simple pleasure that you'll get from having them.