Hello all, Brand new here. Have decided to stop letting life get in the way and start flying. I'm 56 yrs. old, 6' 4" tall, and 240lbs. A local flight school uses the PA28, another school 45 mins. away, is a Cessna Pilot Center and  uses the 172. Any advice on which aircraft would better suit me?

The PA28 comes in a few engine sizes.  You'll need a bigger engine due to your size.  Find out what is available in 180HP+.  The basic PA28 and C172 airframes are similair in size, but you might want to crawl in and out of each one to determine which fits you best.  They are both good aircraft.  The high wing vs. low wing argument is not worth pursuing.  You may want to even check out a C182.  Most small training aircraft cannot handle much weight.  You have to fit yourself, your instructor and fuel.  Check out what's available and talk to the instructors about it.