The lunch on SQ25 is pretty substantial and basically indistinguishable from an SQ dinner service, at least in Suites -- it includes the full service with satay, caviar (or another appetizer), soup, salad, main, and dessert. Not sure what the SQ325 service is exactly but I don't think it's any more, anyway. That said, if I was starting in FRA and going to SIN, I think I would personally prefer the SQ325 timing for being easier to get to sleep.