I purchased the HTC One Developer Edition because I wanted 64GB of storage on T-Mobile and no bloatware, and because T-Mobile told me that I was in a refarmed area. After using it for a week, I'm returning it. The service has been terrible, and I rarely see a 4G connection. I called T-Mobile about this and they said that just because an area has been refarmed, doesn't mean that 1900 is available everwhere. I'm in a refarmed area, but my phone almost never shows 4G, and regularly loses connection. I've never had this issue with another phone on T-Mobile, so I can only attribute this to the lack of 1700 support. It looks like I'll be stuck with a 32GB version from T-Mobile, unfortunately.
To the OP, I don't see a difference in price between the two phones of the same size. The 32GB HTC One is $579.99 at T-Mobile, and the 32 GB Developer version is $579.99 from HTC (Letstalk).