how much was this significant advantage in time?
Depends on the project, how big it is and how the files are organized.
The MS linker has never been very good with really big projects, and even relatively small changes are an issue when you do something 100x a day.
The advantage wasn't really manifest until fairly late in the cycle and there is the tool familiarity issue with PS3, the number of people who dislike the standalone debugger probably out weigh the few people who like it. Which is pretty much what triggered the move to the Vita model where everything is in Visual Studio and for the most part look just like the native tools.