From experience I can only comment on the GTI and Explorer.... and Explorer wins hands down. The Garrett is good detector but the Explorer does everything a bit better, or a lot better. I can probably answer any questions on one vs the other because it's the two detectors I know well.
PS... My friend the Patriot (member here) gave up his DFX about 5 years ago to join our Minelab swinging crew and has never looked back. Mainer, another member here changed from an XLT (similar to DFX) and also has never looked back.