Well, I looked up both lights - or I should say I TRIED to look up both lights... I can't find the MarsHydro TSW3000 but found their 2000 ... I'll just give some random thoughts and you can take it from there:
-MarsHydro doesn't give a whole lot of information on their lights... for example, AC Infinity could tell me the number of LED chips (1024) - MH didn't.
-You are able to place the driver for the MH outside your tent but you can't with the ACI.... in the summer, when heat is a problem, this might be important
-Both have Samsung chips which are great
-I have an AC Infinity tent and I'm REALLY impressed with IT'S quality but that says nothing about their lights...
If this were MY choice, I'd have a hard time of it, too... But I think my bias would lead me to the AC Infinity - they're far more forthcoming about what actually is inside their equipment and even though theirs is the higher cost (I think... at least higher than the TSW2000), I think I would trust them just a bit more... gut feeling only...
Tough choice... good luck!