LTwo issues with titanium. First, it has a higher density than aluminum which means that for any given volume of metal, titanium is heavier. Companies tend to use less titanium for each cooking pot, cup, etc. than they do aluminum but still, aluminum is lighter if the are of a similar thickness.

Second, titanium is an absolutely awful material to heat. The heat transfer is significantly lower than aluminum which means it's harder to cook with. If you are just going to boil water, a titanium vessel will work okay . However if you are going to try to actually cook with it, it's not that good. It has too many hot and cold spots.

I have the MSR Quick2 for trips with others and a MSR Quick1 (titanium) for solo. The Quick2 is a better set.