Generally, with few exceptions, the lower the school is ranked, the lower its national pull. In other words, lower rank = more regionally specific. If you want a more comfortable shot at mid-law, a higher ranked school would probably be your better bet.
The REAL question is, what can you afford? If you go to a lower ranked school, you'll save money, but you'll start at a lower average salary. You need to be comfortable entering at that low salary before you start. It doesn't mean you CAN'T hit mid or big law from a T3 or T4, but your chances are substantially reduced the further down the USNews ladder you go (again, with a few exceptions).
Even a "decent regional firm" will be difficult to hit in a congested market where T3s are competing with a few T1s and T2s. If they're in less congested markets, or ones where they're alone, then your chances rise considerably. You need to be more specific about the schools you're choosing between.
Isnt it all relative though? If you get top 15% of your class, regardless of where you go, you should be able to get a decent job anywhere. No?
Umm, maybe. But the point here is that, were you to attend, say, Catholic in DC, you'd NEED to be top 10-15% to make BigLaw (or probably even most of MidLaw), whereas you'd only NEED to be above the bottom third of the class at Georgetown.
Rule #1: Never count on being top 15% at any school. Ever. No matter how well you did in everything else you ever did before. Ever.
I keep asking questions about the top 15% of a class, or making statements and everyone automatically assumes that I am talking about myself or trying to say I'm going to be in the top 15% of any class at any school I go to. I am not holding out some false hope that I am going to go to law school and get straight A's, I hope that I'm not coming off sounding like that. That would be utterly douchey, cocky and arrogant. I do not know what law school is going to be like, I am just looking forward to it.
But, I think that if you want something, and you try hard enough at it...you can do anything you want. Top 15% anywhere.