Is this for hang-and-hunt style hunting, or would you be hanging and leaving the stand?
I have not used a hawk stand, but to me the cast stands biggest advantage is noise, especially if comparing to an aluminum stand--any of the cast stands are noticeably quieter than any of the welded tube/grate stands that I've used. My guess is the millenium stands are quiet as people rave about them, but you'll pay for it in weight.
I wasnt really familiar with the hawk stands so I looked on their website--Are you talking about the standard size helium, or the helium ultralight, or one of the other heliums? I see both mentioned above...I believe "helium" refers to all of their aluminum stands and they make at least 3 different models. The ultralight is an exceptionally small stand--especially front to back, which to me affects comfort while sitting much more than width. The standard helium model is much larger. You compared to novix--the helium ultralight would be even smaller (and heavier) than a novix Helo, both are a bit smaller than a xop vanish evo or LW assault2. The helium XL appears to be most similar to the novix echo, xop air raid and LW alpha. Hawk msrp pricing appears to be closer to XOP. I do see that novix raised their prices, making them about $80 more than the equivalent hawk stand.
Bottom line, if you're looking at a lighter stand and worried about comfort, look mainly at the length of the platform. 26-28" is going to be on the small side and will be in the 9-11 pound range in most cases, if you're tall you wont be able to stretch your legs. A stand shorter than this is going to feel tiny. look for 30" or so if looking for a comfortable stand, these will mostly be in the 11-14lb range, with some of the boutique brands in this size under 7 pounds. You can shed a little weight by getting a narrower stand, especially toward the back of the stand where it hits the tree, because you dont stand back there and that doesn't really affect your comfort when sitting all day at all. I don't personally worry too much about the difference of an inch or two in width of the stand, as that only affects maneuverability when standing and I feel is not a really big deal even with my monster insulated boots on.