I used my Border a little for tracking when he was younger, but never really had the work for him to get beyond the basics. Was out last week on the Sika hinds with a guy who used two Lakelands and a Lurcher for following up on Sika in the big forestry blocks north of the border and they were very good. They were used seperately I might add, not as a pack before someone comments!
The main difference was that he worked them *alot* and dogs had a lot of practical experience. It was probably fair to say we used the dogs when perhaps a more determined search by the stalker would have turned up the carcass, but as they worked so well, why not?
From my limited experince with my Border, their main down side was that he was too small to work really rough ground such as deep heather or boulder fields. He would get through it, but a bigger dog would cope so much easier. The other down side is I failed to break him to rabbits at a young age. If I were to use a terrier for deer work again, *all* other fur and feather would be off limits. But that was my mistake, not the dogs...
On the plus side, Borders have a great character and are very much a big dog in a small body. They will also be reasonably obedient if taught early in life; well for a terrier anyway!
If I had the work for a deer dog, I would invest in a Garmin Astro GPS Tacker Unit
Astro -A brilliant bit of kit that takes all the hassle and worry when working a dog like a terrier or hound off the lead..They are expensive but if you're using your dog a lot for this kind of work, I think they are worth it...