Hi IvanII
Your question is difficult to answer except in more of generic terms. Basically, the TDI and the GS 5 are quite similar in general specs. The reason is because the fundamental design of the TDI is based upon the GS 5.
Now, are there differences? Yes, but the exact differences are impossible to state simply because of the constant evolution of both detectors and the fact, both designs are not public information.
What you can expect is reasonably similar depth capabilities between the two detectors providing they are adjusted the same. This is where the difficulty lies and it isn't based upon the differences or similarities but upon the characteristics of the design itself.
To try to explain just what I mean, one can get significant differences between two of the same detectors just by how the detector is adjusted. Lets say you have two TD's and you want to detect mini balls at a known Civil war site. Well, the depth of detection of the balls can vary simply because of the ground balance adjustment. Since the mini ball can change tones when the GB (ground balance) control is adjusted, (at least some of them do) then there is a precise point where the mini ball will cause a minimal signal. So, if the GB is adjusted to that point, where there is minimal signal then one may not see much of a depth capability, but another person with a different GB setting may be finding the same targets at extreme depths.
Keep in mind the GB adjustment can help determine targets as well as allow an operator to ignore certain targets. This ability to differentiate or discriminate targets is both a blessing and a curse. The key is to know this fact and just what can happen. If a person does know this and uses it to his advantage, both the TDI and the GS 5 are very unique PI's with tremendous capability.
The true key to getting the most from either detector, the TDI or the GS 5, is the knowledge of just how the detector works and what happens to different targets when the controls are adjusted.
So, once again, if all things are equal, you will not see too much difference between the TDI and the GS 5 if both are adjusted very similar. The GS 5 does have a few features not found on the TDI plus it is hand built by Eric, which means it is precisely adjusted.
The GS 5 is designed to be chest mounted while the TDI can be mounted on the shaft or chest or hip mounted. Now, I built a simple U shaped bracket which allows me to quickly mount my GS 5 on the S handle in about the same location as where the TDI is positioned. So, Now, I have similar capabilities, or at least did have when I had that setup when modifiying another GS 5 owner's detector. I do need to get another S handle and make that change to my present GS 5 when time permits.
I am not sure I have answered your question because, as Mr. Bill as stated, it is quite difficult to do so because of the terrain, but more importantly, because of the capabilities of the detectors themselves.
Reg