The website
HailStoneSoftware has performed a test in order to determine how important ram is when running applications under Rosetta.
But unlike most other test, he focused not on performance level, but rather on memory usage when applications were opened.
The result is really interesting, since most non-universal binaries application running via Rosetta on a MacIntel will request between 1.5 to 3.77 fold more RQM than when running on a PPC-based Mac
Safari that runs fine with 14.8MB RAM on OSX PPC, will use 53.52MB when being emulated via Rosetta on a MacIntel.
So, if you move to MacIntel but still rely heavily on PPC-based applications, you rather get as much RAM as possible.