The serpentine setup will be better, as it handles higher output alternators and also is self-tensioning.
That said, I run 3 v-belts on my '66 289 daily driver (1 alternator, 1 power steering, 1 AC), tighten them about once a year, and have had no issues even running the motor up at high RPMs for extended periods of time. So, whichever floats your boat, really.
Incidentally, I live in Texas and have sat in traffic in heat upwards of 110*F with no issues. I have a stock rad support, a 2 row aluminum radiator, an otherwise stock cooling system (including 195*F thermostat), and my motor is knocked out 0.040" over and is not terribly stock. It shouldn't take anything radical to keep our cars cool. Some find that for cars that sit in very heavy traffic for long periods of time in hot weather (something you would see in Atlanta, for instance), an electric fan is the best solution because they can pull more air through the radiator while your car is idling than a stock mechanical fan can. But I don't know, I've never needed it.