Well as the old saying goes "you get what you pay for" at least that is the case more often than not. Here is my general rule of thumb for how I decided.

As for free websites, sure you can get a decent amount of information. Yet you have to belong to quite a few different free websites to get even a fraction of all the information that one pay for site has. Which also increases the frustration factor because it can be hard to remember what information was where or if you are even getting the full picture. You just need to remember, you are getting free information so anyone can usually add to it without any need for expertise.

Onetime fee websites can be helpful. They are definitely full of information 9 times out of 10. Although the problem that I have always run into is they seem to bombard you with information but once you get through it... that's it. What is their incentive to keep updating their information; they already have your currency. Do not get me wrong, they can be complete and full and they are definitely useful for information that does not change a lot (like a tutorial for a certain program) however just be careful when it is something that is constantly changing.

Reoccurring subscriptions is always what I like. They are usually the ones that have a "contact us" area and answer questions promptly. They update the information as often as possible to keep people coming. They also usually offer a lot more and keep giving you a lot of information because they want you to stay with them so they can keep getting more cash. Granted that is a bit greedy, but let's face it... currency talks. Would you be more willing to help someone for free or if they paid you? Which would you be more thorough with? Paying customers! The other bonus is that the reoccurring subscription is usually cheaper than the 1 time buy, so you can test it out for a bit to see if it's worth your time instead of diving into something else that would have cost you double, triple or more.