The first question is to ask yourself what makes a trusted system. Depending on one's standards, beliefs and experiences, anything can be trusted (which is probably why you feel overwhelmed with all of the options and opinions out there).
What is important to you? Pen and paper are great (no crashes/fast boot up/no batteries to keep charged/low start up costs), but they are harder to "back up."
Apps are plentiful. Which operating system(s) are you on? Your chosen platform will affect your choice.
Are you always online? If not, web apps would be right out.
I use a Mac, an iPhone and an iPad. I chose
TaskPaper, as it makes me feel like a captain and commander. My lists are in a plain text file (syncs and back ups are almost instantaneous), so in the unlikely event that TaskPaper's developer ever moves on, my system will not miss a beat.
If you are overwhelmed with the myriad options, I'd suggest starting with pen and paper. They have stood the test of time. There is something serene about sitting down with tactile tools in hand, disconnected from the 'net and notifications.
If you give pen and paper a solid try, and find that they don't work for you—your time will have been well spent. You will know the core of GTD and what parameters to look for in an app.
To minimize your overwhelm, take a look at the
setup guides that the David Allen co. offers. Pick the one that meets your needs and that feels right (listen to your gut instinct). Then buy it and embrace the instructions.
