If you are buying new then you should buy from a place that will be close and give you service after the sale. If that is not part of the purchase you are wasting money IMHO as a good part of the purchase price is paid up front for adjustments and service in the short term once you start riding it. If that is not part of the picture you are much better off buying a bike that is a model year old or older if new or several years old and slightly used if you know your size and needs.

If the purchaser is not capable of doing his own wrenching then buying from a local shop is much more important than buying by brand loyality since as you say groupsets are the same across brand lines. First find the shop, then find the bike.