Brass radiators are easier to repair as long as the metal has not been corroded away, making it too thin to solder or to retain enough strength.
Plastic tank repair kits are available and work if just sealing a crack or small hole. I have used them several times and never had a patch go bad.
http://www.2wheelpros.com/permatex-radiator-repair-kit-2359976.html?gclid=CM35sJae9rcCFU_ZQgodIA8AlQ
When I was growing up in the 50s and 60s, radiator problems were very common, much more so than today. You did not see many radiators last 10 or more years without major repairs.
I know of several 1997-2000 XJs with the original radiators. My 13 year Acura run cools on its original, trouble free plastic/aluminum radiator.
Coolants are much better today. Engines, and cars in general, have better anti-corrosion engineering.
That said, my XJ has a brass radiator but only because thicker core radiators are only available in brass or aluminum.
When it come to resistance to pressure, aluminum wins hands down, one of the reason why racers use them.
IMO, most radiator problems are the result of poor maintenance and improper coolants.