I'm glad you've read the eBook and hope you've learned something from it. Although it was written for the X-TERRA series, there are some techniques in there that should help just about anyone who enjoys the hobby. As to the ATPro.....I appreciate your question, and your comment that you are not making this post to start a war. I don't want to do that either. Both are excellent detectors. And folks are having remarkable success with each. But with that in mind, let's take a look at some functionality differences......
We recognize that higher frequencies are "more responsive" to lower conductive targets . And, higher frequencies are better suited for very small targets. Lower frequencies are better suited for higher conductive targets. And they are more responsive to larger, deeper targets. The ATPro operates at 15kHz, which works well for most jewelry and coins. But the X-TERRA has the option of operating at 3 kHz, 7.5kHz or 18.75 kHz, depending on the coil you are using. This allows you to set up your detector for specific types of targets. That is not to say all frequencies don't hit all target properties. They do. But the audio response that it provides on specific targets is much more defined, when able to adjust your operating frequency. The ATPro offers three response tones. The X-TERRA offers 28 audio tones, one for each notch segment. That allows me to "hunt by ear" without having to look at the screen to confirm a target response. And it isn't just the pitch of the tone that is provided....it is the manner in which that tone is produced by the detector. Harmonics, sharp burst, a whisper, solid blast..etc. With some practice, you can learn as much about a target by the sound of the tone, as you can the pitch.
Although the ATPro has more TID numbers, I don't rely solely on numbers. Especially when searching public areas for gold jewelry. As I'm sure you know, numbers don't tell the whole story.
There has been some discussion on this forum regarding recovery speed. In my experience, I'd say they are pretty equal to each other......and way ahead of many detectors. Especially when you are looking at reset speed in and amongst the trash. Both work well using a fairly rapid sweep speed. But I find the 705 to lock on to partially masked targets better than the ATPro, due to it being able to separate well at slower speeds. That doesn't mean both don't separate targets. But I've found the X-TERRA will lock onto good targets with more authority, in nasty trashy areas.
The X-TERRA offers many more settings for Sensitivity, allowing you to "fine tune" your detector for the site. Similarly, the X-TERRA offers more options to maintain the proper ground balance. (tracking, beach, tracking with offset) Even the ATPro manual suggests that running with a positive gb can enhance detection of small targets. And a negative offset can reduce the effects of hot rocks. But with the ATPro, the only way to do that is to set it and hope the ground conditions don't change. With the X-705, I can literally "set it and forget it" when implementing Tracking Ground Balance with an Offset.
The X-705 offers standard Pinpoint and Sizing Pinpoint. I find Sizing Pinpoint (and Prospecting mode) to be a great tool when isolating (and sizing) adjacent targets in trashy areas.
The ATPro can be used in water.....not so with the X-TERRA.
Again, both detectors are excellent choices, and each has it's following. I know you said you've hunted for 20 years.....but before I could make any recommendation to you, I'd want to know what you mean by "better" for parks and grounds? Target separation? Depth? Audio tones? Target ID? What coils do you hunt with? With some additional information, I will give you my honest opinion. Thanks again for your comments and question. JMHO HH Randy