The Unitab website lists two sets of selections for some meetings. One is a specialist tipster that works for Radiotab. (Today, for example, Ian Humphries at Port Macquarie and Warren Huntly at Wangaratta)

The other tips, called "Radiotab Tips" are simply the tips of the racecaller at each track, and you're right, some have better records than others. In most (but not all) cases, it's the same tipster as that listed on the NSW Tab or Sky Channel websites.

Today, the tipsters would be:
Tony Wode (Town)
Damian Seaton (P.Mac)
Rick McIntosh (Wang)

Another point I must make is that unfortunately, you can not absolutely rely on 100% accuracy with those "Radiotab tips". Whoever it is that puts the tips up on the website has actually made a few mistakes over the years. Just last week, a real roughie (number 2) was supposedly tipped on top in one race, but I checked on another website and it was really supposed to be number 6 or something. I wonder how many people were fooled by this and put number 2 on, thinking it was great value for a top selection.