With a 53% groundball rate (per Ron Shandler's Baseball Forecaster) and 198 Ks, Ubaldo Jimenez logged a xERA of 3.31. His ERA was 3.47.
Jorge de la Rosa had a perfectly acceptable 45% GB% with 193 Ks (Ron Shandler's BPV calcuation gives positive credit to GB%>40%), but logged a 4.38 ERA. FF's xERA was 3.56 though.
With a H% of 32 and a positive xERA differential, de la Rosa appears poised to surprise. Ubaldo's H% in 2009 was 29%. That, alongs with a much smaller xERA differential in 2009, signals a worse season in 2010 for Ubaldo.
NOTE: My earlier comparison of both pitcher's using Baseball Prospectus' stats came to a similar conclusion despite much high GB%s.