Actually, I think we shall do the math this way.
6 stays(nights) at aloft/4points
=You spend$480
=You earn less (960pts)
So give up 960pts you loss a half night at cat 1

You gets
3nights at St.Regis / W (Cat 5/6)
=You earn extra 1500pt welcome pt.
=$1200 worth of room charge
=get upgraded by luck ($600 per suite)

why even care about a half night at cat 1

Come up, go and get a room every 2days in the cheapest aloft/4 points near you. Think about it, you actually get 3 nights at aloft and 1 1/2 nights at Cat 5/6 for the price of 1 night, which you originally plan to stay. Plus, think about the extra welcome points you will get by check in / out extraly. It's a lot more than double pts.
swimming every two days in an aloft/4points and get your breakfast and evening cocktail for free.

If you are not targeted at this promo, go revenge. Eat and drink more in the lounge. Boost up their hotel cost.