Basically they said the main issues were that the Brose motor has so many ports for different things like lights etc.. which could lead to water getting into the motor
The Brose motor is an off the shelf motor designed and made by brose and is used by various other manufactures, the only difference for us is that it has Specialized firmware on it, so there isn't much Specialized can do to combat any water ingress apart from informing Brose of the issues the UK faces and speaking to dealers about how best to look after/wash and maintain the bikes and the dealers should pass this information on to the customers
Spoke to their main technical guy (sorry cant remember his name, nice bloke though) and he said that here in the UK were are quite unique in that we ride all year round in all weathers which the majority of riders in other countries don't do due to not having our kind of winters (mainly wet for us) or the fact that most riders in other countries don't ride in wet conditions due to trail damage
We are in a unique position in the UK that we can ride all year round in all conditions, Specialized UK realise this and do pass all the information about water ingress issues etc... back to the development team in Switzerland
The new SL motor has been designed by Specialized and built by Mahle (with some of their input) and Specialized have addressed some of the water ingress issues, for example the SL only has two ports for this reason, the power plug is higher up on the bottom of the seat tube, it is spring closed with a catch which has a sucker on the inside to stop water getting into the plug area
They did say that the Brose motor is here to stay and the SL motor will run along side it, there are no plans for them to drop Brose
Personally i think that in a two or so years they will take the SL motor and scale it up (power wise) to fit the next generation of Levo and drop Brose altogether, that makes sense to me and im sure they would like to have their own complete system (the Levo/Kenevo system of battery, Brose motor and TCU are made by three different companies) on all their range of bikes
Also it seems we are pronouncing Brose wrong! going by the Q&A session they pronounce Brose the same way you say Rose wine (Brose-ay)