No question, the White's IDX is awesome for heavy trash with a small coil. I used one extensively with the 6 1/2" concentric coil and it was great. I am a park/school hunter and it was always in my trunk as my second detector for when I got into the heavy trash. Plus, it's a classic White's analog design with the knobs and heavy duty metal box. What's not to like?
The IDX ruled in the trash until I bought a Gold Bug Pro. I bought the GB Pro for nuggetshooting but soon discovered it did pretty darned good for coins too. Not only that, but I soon noticed it had a heckuva recovery speed to boot. SO I did a fair amount of head-to-head testing of my IDX with my GB Pro. The IDX was definitely a little deeper, especially with the adjustable ground balance mod, but here was my unmistakable conclusion: the GB Pro was consistently better for recovery speed and separation in the trash! I did tests in a variety of soils and with a variety of targets at different distances apart and buried targets too. The GB Pro was distinctly better than the IDX for target separation in heavy trash. The IDX still got better depth, but my XL Pro gets even better depth than the IDX and the XL Pro is what I use until the trash gets too heavy, then it's all about recovery speed and out comes the backup detector with the small coil.
In the end, I reluctantly sold my IDX and bought the larger DD coil for the GB Pro to compliment the stock 5" coil. Now my GB Pro does double duty as my nuggetshooter PLUS park/school heavy trash separator. The IDX ruled the heavy trash areas for many years, but has finally been dethroned by the GB Pro. Try one and you will be simply amazed at how good it is.