Diad 5 is too small and light to be used as a last line of defense against dogs unfortunately. The menu is almost exactly the same as the 4. My main complaint is with the touch screen being required on some transactions because I sometimes wear gloves.
You don't need to use the touch screen and I never do because I always end up missing and pressing a function that I don't want. All you do is hit the yellow button and this assigns a number or letter to each option on the touch screen. It becomes second nature after about 10 stops. For example I scan the package, big arrow down, hit the yellow key, this puts a 5 next to "deliver", hit "5" and then "7" for front door, "1" for MCM, etc.
The only time this won't work is if you're out of the GPS area and the board is red and going off. You have to use the touch screen here. In other words, if you're not at the stop you need to use the touch screen to sheet the package. I'm not sure why.
Also the keys are raised high enough so that they are actually easier to use with gloves than IV.