In any situation where you have reception problems, the more bands you can use, the better. The iPhone 4 (and 4S) can only use T-Mobile's signal on 1900 MHz (2G & 3G). When this band becomes congested, there's no alternative. While all that the iPhone 5 adds to this is the AWS band, that's a big addition. While right now, LTE adds only improved data, VoLTE is right around the corner and will add yet another voice path.
Having said all that. There really should not be and outside dead spot in Brooklyn and the engineers should learn about it.