The screen on the current model (Dana R) is not great for readability. It has supposedly been improved on the new RS model (which I have not seen). However, screen legibility should not be an issue because the pump is designed to be fully controllable (ALL functions including cartridge loading etc) remotely via Bluetooth from a mobile phone (or a dedicated remote controller). At present the App is only available for Android, but a version for iPhone is supposed to be released shortly. For Dexcom, you can send your G5 readings direct to the phone using either the Dexcom App or Xdrip+ (for Android only). Thus you can control your pump, and have your CGM data on a single device.
For me, the attraction of the Dana (and I am going to try to get one to replace my just-out-of-warranty Vibe), is that it will run Android APS, which is one of the DIY hybrid closed loop systems (actually a variant of OpenAPS). The other loop systems onlly work with “heritage” (x22) Medtronic pumps and need DIY soldering and programming of hobby microcomputers and radio links. With the Dana + Android APS all you need is the pump, Dexcom G5 and an Android phone.
If you go with the 630G, of course you can use Dexcom G5 and send the readings to your phone (or a receiver), but you will not get the low glucose suspend feature of the 630G unless you use Medtronic’s sensor.