To Diet Coke or not to Diet Coke

I go through phases where I just don't feel my lunch is complete without downing a can of Coke. I love it, whether it's diet, zero or full sugar it just makes my lunch that bit more satisfying. Lately I've been going the zero/diet Cokes as I am trying to cut my calories but I am always questioning myself which is better. There is so much research that tries to prove that artificial sweeteners are harmful, or studies that show diet drinkers gain more fat than the full sugar drinkers. I go from full sugar to diet and so forth after being scared off by the ever growing amount of research on the subject. One thing I know for sure is that drinking water instead is the only real solution but where's the fun in that? What is it that makes me crave it? It's obviously not the sugar and I doubt it's the caffeine as I am not addicted to coffee. It could possibly be that my lunches are boring and need a dousing of caffeinated goodness to wash it down...

When I do some Googling I find that Aspartame, the sweetener in diet sodas is apparently a pretty lethal substance. But this info is always on a wellness or alternative style medicine site. If you read about it from scientific research there has been over 200 studies since 1967 and it is still approved by WHO (World Health Organisation). Each side has their own conflicting studies as well with the wellness people claiming diet soda drinkers put on more weight and the scientists claiming the opposite. In my own observations I honestly notice that it's usually the overweight people drinking the diet soda and the slim people drinking the full sugar soda. Shouldn't it be the other way around? 
Today I read that a British study has shown that both diet and full sugar can cause increases in blood pressure which is another woe that I will add to my list of diet soda woes. I'm still going to keep drinking it though. At about 4 cans per week I don't think it's having a negative effect on me, I'd just like to know the truth!
-Lucas