We use both iPhone5 and the new Rand Mcnally . They both have their place and separate benefits. As stated, getting the RM set up correct if or your needs is key. Coming from Garmin was another learning curve but at this point we have developed a lot of trust in what RM does now. No nav is perfect!
Just FYI. DW will use iPhone sat image up ahead of us to understand which stations or exits we have ease room for our rig. RM seems to have an edge over iPhone finding WalMarts and helps to find which ones do not allow RVs or gives you phonenumberto call and check.
Before you buy the iPadversion I would call RM and find out what might be diff in operation. I.e. does iPad version need an active data signal to do a rerouteorother items....