Having reread this thread, and I accept being biased in favour of the PDA solution, I have to conclude that PDAs are less reliable. If you want a guaranteed solution any of the better dedicated aviation products are likely to be sound.
However, to defend my original position, PDAs can be as reliable or nearly as reliable. Their problem is that you need to do some research before buying and have an understanding of PDAs potential gotchas to achieve equivalent reliability.
In short if you read the specialist forums such as PocketFms you will find there are certain PDAs that are favoured and certain combinations of PDAs and receivers that work well.
Personally, I have used an HX4700 with an extended battery and SD card with a great deal of success. I have yet to have a failure or have the unit “hang” in operation. Battery life is in excess of three and a half hours from a full charge and most bluetooth GPS receivers will run for considerably longer.
I agree with Bose in disliking yoke mounted GPSs. However, infact that is another reason for favouring a PDA. With a couple of bits of velcro they can be mounted on any yoke or convenient spot on the panel without being cumbersome.
Finally, with PDAs becoming so cheap in the second hand unit, carry a couple with you, so if one fails or runs out of power for any reason you have a backup!