If you have a good mount or a firm holder mount for a large phone or tablet and a better tablet such as a Samsung or LG or similar that has a good quality GPS unit, Samsung now has GLONASS as well so can hold a stronger fix.
Some swear by Google maps but problem is you need to be online or cache the maps of area first before a trip as not all tablets has Sim and Data capability. Also data costs in most country and using Google maps all the time can be expensive unless you have a huge Data pack or unlimited Data.
So then we look at apps that store the maps on SD card or in phone/tablet memory. There are many available and and all have thing for and against. They are getting better and some mach or exceed a stand alone GPS unit.
There are three that stand out due to their use, graphics, and quality of maps and the main point to take account of is ease of address input and poi information that the map supplies.
The first is iGo Primo for both Android/Apple, does cost has great 3D graphics heaps of info, lane assist heaps of poi's and many extras. The second is Navfree on Playstore/Android and is free. Not as polished as some but still a great app with all info and is FREE.
The third and my favorite which is what I use is Sygic playstore/Android. (free to try/one off lifetime cost) has fantastic 3D graphics with 3D buildings, TTS speech and everything else that's in expensive units. It also has a very comprehensive poi list with all fuel stations and live traffic info for those that connect to data via their device.
As far as hitting wrong buttons and returning to tablet from GPS as Bob mentioned is very hard as most GPS apps will pop up a screen with quit GPS yes/no. and that's only if you hit the exit button which is usually in the menu and you have no need to go to menu while driving. your destination should be input before driving off and there is no need to touch the unit after that.
Any info need to be used on GPS is contained on main screen maps via a touch and big buttons that show. Once you select what you want to see the unit returns to map screen automatically after a certain time, usually 15 seconds.
The apps basically work and respond exactly as the stand alone units do. Its just nice at end of trip to un-clip your 5 inch phone and put it your pocket instead of leaving it in the car to be stolen.