If you have both cards, all your regular MR points convert to MR1st points (which have a better redemption value). I'd say apply for the platinum and keep your PRG.
As of 1/10/2014 EX FICO - 748. EQ FICO - 728. Trans FICO - 755
WellsFargo - $3,000 AMEX BCE - $18,000 Chase Freedom - $4,000