If totally new to Shadowrun there's another reason to use the 400 BP (even if the PCs are still new to running the shadows) which is; Most pre-made modules/adventures/runs will have the 400 BP in mind, so if the GM is also new and uses pre-made runs then you run the risk of higher probability towards TPK.
Another way to limit the "experience" of the PCs at creation is to drop the Attribute/Skill max's down. So instead of only one skill starting out at 6, it's now 5, and so on, And this can also be carried over to equipment, programs, equipment availability, etc. Players can then be encouraged to spend that "extra" BP on rounding out skill sets, buying more contacts, etc.