I use STD mode on the AT Pro but I wouldn't say "routinely". I've also done a lot of detector comparison with the AT Pro in one hand (in STD coin mode) and the ACE 250 in the other hand. I realize they are quite different detectors but at least they are both operating in "binary audio" mode so any targets are always strong beeps. There also the the difference in DD vs concentric coils. Anyway.... For the most part, both detectors could see targets equally well and ID them almost the same. I was surprised to find that each detector was capable of finding COIN targets that the other one had trouble with.or missed altogether.
I started out expecting that the AT Pro would find targets that the ACE 250 was not capable of and while that was true, I was surprised surprised that the ACE also locked onto targets that the AT Pro didn't detect. I can't say exactly why that might might be. Different coils, different frequencies, different tuning, different ground balancing, etc.? All I can really conclude is that they are both good detectors, but each has it's own personality (for lack of a better word).
As far a using the AT Pro in STD vs Pro mode. I would say it's pretty obvious that the AT Pro is significantly more sensitive in PRO mode and that proportional audio gives superior target information (once you learn to interpret it effectively).. I find that when I use the AT Pro in STD mode I end up digging a lot more junk because the binary audio always gives the strong tones even on that turns out to be junk targets. So, the down side of STD mode binary audio is that I probably dig more often than necessary. But.... the up side of binary audio is also that I dig more often than necessary and probably find more stuff that I might have passed over in PRO mode being lazy about digging.
I think in the final analysis, a few things stand out in my mind.
1. The AT Pro in PRO mode is much more sensitive and will surely find more targets than STD mode.
2. STD mode is quite nice, is fun, and will find lots of good targets and is the best way to learn if you're new to detecting.
3. Regardless of the mode, dig all those targets and you will be rewarded. If your not digging significant trash, you're missing some good stuff.