I have used both a carto tank and a REO. Can't say much about the leaking issues of the tank. Since I own a Chibi tank and the grommets are on there very tightly. So, I never got any leaks from it. There are advantages and disadvantages to both depending on what you find important.
So it really depends on what you would prefer in the end. Carto tanks main advantage is that when you take a draw. Then it automatically feeds during that time or when the filler material is a bit dry. Which will ensure that you don't have to top it off at all. The downside is that sometimes you have to give it a rest for it to soak up the liquid that's in the tank. This can be a problem if your tasting that it's dry then there's no immediate solution. Meaning that you have to wait and do some primer puffs to get the juice flowing again.
With REO's, the main advantage is that it doesn't have this problem. So, if your feeling like it's tasting dry or there's a decrease in flavor. Then all you have to do is a couple of long dry squonks and your back in action. Which means that you, as a user have complete and utter control of juice that flows into your cartomizer. Feeding it manually can be seen as a negative. Personally, I don't have a problem with this and tend to like this feature compared to a carto tank.
All in all, both are fairly consistent when it comes to performance. I'm going to leave it at that and let you decide on your own on which one you like the most.