If you go into business for yourself, your degree won't stop you from hiring yourself, will it?
It may be harder to attract clients who may want the prestige of a "Hahvahd" trained lawyer at their beck and call.
I think that a good general rule of thumb is to think about it this way. How are you going to stand out and be attractive? A prestige degree does that for you automatically. If you pass up the prestige (like I did), then you need to have a solid plan for getting to where you want to go. In my case, I am doing very well at my regional T4 school, and don't plan on leaving the city, and have enough legal experience as a paralegal to know the right people to help land a job in public interest (which is what I've always wanted to do). So for me, with all of the factors, taking the money at a T4 was better than going up the road to the Top100 school for less financial help.
But again, if you don't have a solid plan to make yourself attractive regardless of where your degree is from, then you might want to consider taking the best school you get into.