I live in Iowa and hunt in those same type places. And, I have them both. I think the X-50 will hunt as well as the X-70 in most situations. And I won't say you will dig more coins using the X-70, opposed to the X-50. But over the past couple years, I've gotten so use to some of the additional functionality of the X-70, it would be hard for me to go back to the X-50 on a regular basis. Here are some of those "reasons".......... 1. I hunt in all metal mode, with multiple tones. 2. when hunting in the multiple tone mode, I get a much more distinct set of tones on deep iron, using the 3 kHz coil. 3. I rarely use the Pinpoint mode, instead opting for the Prospecting mode for both pinpointing and target sizing. 4. I get better target definition using the 2-digit notch segments of the X-70. 5. the "auto modes" of the X-70 make it much quicker to set up the detector, when arriving at a new site. 6. the tracking feature helps insure you are keeping your GB accurate when hunting open fields.
Like I said, I don't think you'll dig coins any deeper with the X-70 than a properly set X-50. But I'd almost guarantee you'll dig less trash (for the reasons highlighted above). JMHO HH Randy