I own the ATX and have only read on the TDI. These are my take on both. I have no way to compare performance, other than to say I have the Whites SurfMaster (since 1994), the Garrett Infinium (since 200
and the ATX (since 2013) and the ATX is the pulse detector of my choice. My choice is mainly due to the control features of the ATX which I believe to have contributed to my enjoyment in its use over my other PI detectors.
If a feature such as Warranty, volume control, low battery indication, etc. are not mentioned they are the same for both PI detectors. I may have miss a feature that is different, so do not assume this is a complete comparison of the two PI detectors.
Advantages of the TDI:
Half the price ($1300 vs $2500-3000)
2 pounds lighter
Hip mountable (supplied with detector - a mesh bag
Better camlocks (IMO - less maintenance)
Smaller shaft equates to less water resistance and less tiring on the wet / dry sand and ground. I have to use a Minelab ProSwing 45 when out of the water.
Yellow coil, easier to see in murky water
Greater submersion depth (25' vs 10')
Coil are half the price of the ATX's ($250 vs $530 or $600) 3 coils: 7.5" Mono, 7.5" DF, 12" DF but do not include NEW shafts and are hardwired.
Advantages of the ATX:
More "package" buying options
Standard AA MiNH batteries vs the custom battery pack of the TDI
Twice the battery life (12hrs vs 6hrs)
Multi-Frequency PI Technology
Quick Iron Check
Quicker control via push buttons vs rotating knobs
Auto and Tracking Ground Balance modes - less or no need to re-balance after after changing sensitivity, gain, or "discriminate / delay"
Motion and Non-Motion operation
Adjustable armrest
Visual indication of settings / target response (LEDs)
Headphones are NOT hardwired easy to change type of headphones I.e. waterproof, land, ear buds and can be set up with wireless
5 coils: 15X20" Mono, 11X13" Mono, 11X13" DD, 10X12" DD, and 8" round Mono. Each includes a NEW shaft and user quick change connector