I believe that breeds with more (or less) resistance is mostly anecdotal; for example, someone suggesting that Breed X seems to be resistant (but lives in Europe) might have a totally different experience than someone that has Breed X but lives in the USA. Genetics, origins, and regional differences are going to have a huge impact. It seems logical that those that import chickens from a different continent are going to find that they might be more susceptible to Marek's strains in the new region for several generations... for example people have reported that Cream Legbars, which have been somewhat recently imported to the USA, seem to succumb to it more frequently.
I know this sounds complicated and frustrating... trust me, I totally feel you there!! I went through this internal battle, myself, when seeking new birds recently. The short answer is that there are almost certainly chickens out there that have higher resistance to the disease (this is not immunity, but a greater resistance) but it matters which strain of the disease they are resistant to in their location. If you can find someone in your region that is breeding for resistance, with good records, and good results, that is probably the most optimal solution. I couldn't find anyone like this in my region. I don't know how many people actually breed for resistance to Marek's and also keep great records?
Finding breeders that vaccinate properly is also tricky. Please see the Vaccination section on the Marek's FAQ as to why many breeders don't vaccinate and why vaccination is tricky (not impossible, but tricky) at home. In the end due to this, I decided to order from a small-time farm hatchery (instead of a large commercial one, that's a whole other discussion but is not related to Marek's) that vaccinates their day old chicks before shipping. My current chicks are now three months old, and I suppose I'll have to wait for another 9 months or so before I can report back on if I was successful with them or not. I hope so, because I love them dearly!
