According to DIN1304 and DIN1313 unit symbols (Ohm=V/A) should be written roman while symbols (R=U/I) are italic. Mathcad handled this correctly but in SMath studio it's just the opposite. It seems to be a general rule for printing SI units according to Wikipedia: SI units

This is filed as SS-48 in the bug tracking system. You might register there and vote for the request.