which one is the best and maybe give some reasons why one is better than the other or there is no difference...

 

I always go with synthetic simply because you don't need to do oil change every 3k miles like the nonsythetic ones. In fact I was told sythetic can last up to 10k miles if you don't drive like a street racer. I only do oil change usually every 5K-6K miles with sythetic. I won't claim it is absolutely better because someone always say something else. As far as I know from what I researched, all synthetic oil also have motor oil additive just like those off the counter oil additive to help improve hp, protect engine, etc. except you don't need to buy those anymore, they are all in one with the sythetic oil.

From personal experience, I have been using sythetic for my current Protege since 75K miles and is now 137K miles. Been replacing oil every 5-6K miles. The good news, it doesn't seem like my engine has any sign of aging at all. My previous car (626) engine performance keep going downhill regardless how much I tried all kinds of good engine conditioner or additive (supposedly claim by all these sales ppl). With my current Protege, all I ever did was using sythetic oil and nothing else. Guess what, my car engine power and performance haven't change one bit since 75K miles. Gas mileage has been consistently the same for me for the pass few years. Engine power hasn't deteriote or gone downhill for me either for the pass few years. I know how an engine performance start going downhill feels like since I have experience it before with my previous car the 626. Besides, I can definitely also feel the difference of engine running smoother with sythetic and maybe slightly more power.

Well that is what I have experienced so far and what I know about it. But again, I am not claiming is absolutely better, but if you ask for my opinion and personal experience with it, I will definitely recommend it and will say YES, it is better.