Here are my thoughts:
Patek very rarely does limited editions. Ok, they ofeten discontinue their lines and hence make very few 2499s, 5970s, 5004s, what have you.
Rolex never does pro-forma limited editions. These are the most collectable brands because they are managed by people who understand that the true connoisseurs want a watch that is worthwhile buying on its own merits. When a brand releases a limited edition I always get the feeling that they are trying to appeal to the nouveau riche.
Also, Patek and Rolex are the best performers at auctions.
Regards,
Joseph