Stag
Both myself and a mate have used GWP's for the last 7 years on both Roe and Sika. I must admit though, that almost all the deer were found on 'wind scent' as we generally neck shot everything but it was still an issue at times finding them when the shot was at distance and they are lying in ferns or long grass.
Personally, if I wanted a dog that may have to hold a wounded Sika, I would think that a GWP would be one of my first choices although Gazza on here has a BMH and told me I may be surprised at what they are capable of.
I think you have to bare in mind what is a regular occurrence to you when stalking. Wounding a beast and needing a dog to have the ability to hold it is hopefully a very rare occurrence. Shooting a Sika in the ribs and watching it run off is a very common occurrence so a dog that is known for its tracking abilities is probably a sensible way to go. However, I have had spaniels that mark and retrieve as well as any lab and also labs that have hunted cover as well as any spaniel.
I think the comment about getting a breed that really appeals to you is important as well. I would also consider what your daily routine is like and how often you actually go out stalking with the dog. I will not comment on BMH's as I know very little about the breed but I am told they do need regular stimulation through work. I feel that when I take out my GWP with my other dogs she runs about with them like a big daft kid, yet when it is just her and me she seems to switch on to the fact we are now stalking and behaves accordingly. As has been said before, all dogs possess an incredible sense of smell and if trained appropriately should be able to follow scent of any kind.