Really. I would get a manufacturer approved remap every day above an aftermarket if it was available, even after warranty, especially if it gets positive reviews. However talented the aftermarket tuners are, they don't full access to all the information and (testing) knowledge that is available, nor do they have acces to all the development tools and parameters that can be adjusted. And even with several rolling road runs, they will not have access to the thorough testing which the orginal manufacturer will do before they sign off the remap.
Sorry but I don't agree with that at all and tbh it comes across as a little bit naive on your part IMO..
I would much rather have someone like DMS/Evolve map my car than some overpriced manufacturer's effort.. Yeah there are some cheap/dodgy maps out there from companies that 'claim' they know what they are doing, but that's normally reflected in the price. So definitely not worth while scrimping when messing with a cars ECU. So always do your homework!!!
Although I have no experience with BMWP ECU upgrade, I would pretty much bet my left arm that it will be a generic map that is just flashed on to any/every car that goes into the workshop for the same treatment by whatever tech is available (model specific of course). Where as when you go with a reputable tuner that does this thing day in, day out, most of them will map it on the rollers and will spend a good few hours fine tuning it to your
For example, Rob from DMS and Sal from Evolve would know 10x as much information on tuning a 135i/335i and it's limits than some random BMW tech at your local dealership. Half the time they don't know their arse from their elbows in my experience..
I have had 3 cars mapped now and done over 250,000 miles between them. All by well respected tuners for VAG, BMW etc and I have never had 1 single map related failure within that mileage. Plus all cars were driven hard with countless runs on the 1/4 mile etc and one being modded to 50% more power than it left the factory with..
The only plus side I can see about getting the BMWP software is that you get a supporting warranty. But saying that, i've never had any problems with my previous cars with any main dealers regarding warranty and know of plenty of others too. That's not to say they're all mod friendly though..