I don't just use Tesoro's but they have well proven themselves in the iron around here especially on old sites. I also use the Gold Racer and Multi Kruzer. Hunt in either disc or all metal modes depending on conditions.

Machines that I find effective are ones that have a wide iron gamut and good sensitivity towards the ground phase range. I have found those machines good for hunted out sites as I can hear the fringe targets as those tend to fall off on many machines. Tejon and Gold Racer are incredibly sensitive in that respect. Cibola has very low iron response making it easy to hunt permissions but at a risk of skipping over fringe targets.

Tejon and Gold Racer have good threshold descrimination that truely trims the signal response unlike the Apex, AT Pro that simply turn off the audio.

Though the AT Pro and Apex can be effective you really need smaller coils for them.

Oddly Makro when they designed the Kruzers they set it with an effective iron range where an iron nail breaks at 4 yet they kept the sensitivity close to ground phase coupled with high gain on TX making them very chatty. Old sites even with a concentric on it can be fair for performance. As a coin and jewelry hunter with the 5 1/2 x 9 dd the Kruzer is an incredible machine and I have been able to snipe out some nice targets but it is prone to masking.

Majority of people are not necessarily hunting the toughest ground or the trashiest areas. Many with the new machines here use them effectively at the beach and why beaches here are sparce on targets as there is an incredible amount of competition.

I spend my time in the worst of places, burn pit, old foundations where the structures had burned down, old middens.
Hunting those areas where there are so many targets is just an exhausting task with modern machines that beep on everything and worse when majority of those beeps are trash. Most of the new machines come with 11" dd coils which here is probably the worst choice.